Start from your design, not from a catalogue
A diecast model car supplier does not sell a catalogue to choose from; it sells the ability to produce your design, and a supplier chosen from a catalogue, without your design's facts, is a supplier chosen for no design, whose ability for your design remains untested. Start from your design: the vehicle, the material, the scale, the quantity, and the market, because those five facts decide which suppliers can produce it, and because a supplier who receives them can confirm for your design, rather than for model cars in general, while a supplier who receives only a product word can give only a general answer, which fits no design.
A buyer who starts from a catalogue will often choose the supplier with the most models, the lowest price, or the loudest promise, and will discover, after ordering, that the supplier cannot produce their design at their scale, in their material, or in their quantity, because the catalogue's models are not the buyer's design, and because a supplier's ability for one design does not guarantee its ability for another. Start from your design, and choose the supplier who confirms for it, in writing, because a confirmation for your design is a confirmation that can be relied on, while a catalogue is a list that cannot.
Check manufacturing capability, not marketing
Check what a supplier can actually produce: diecast metal, plastic, and resin, at which scales, in which quantities, with which mold terms, because a supplier who produces diecast metal may not produce resin, a supplier who produces large scales may not produce small ones, and a supplier who accepts large orders may not accept small ones, and because a supplier's marketing may claim more than its manufacturing can deliver. Ask for the capability for your design, in writing, with the material, the scale, and the quantity, so the supplier's answer is specific to your design, rather than general to its business.
Ask for examples of the same kind of work, not for a client list, because a client list proves past customers, not present capability, and because a supplier's past work for one design does not guarantee its work for yours, while examples of the same material, the same scale, and the same quantity do indicate capability for your design. A supplier who shows relevant examples, and confirms for your design, in writing, is a supplier whose capability is evidenced, while a supplier who shows only a catalogue, and promises generally, is a supplier whose capability is asserted, not evidenced.
Check mold terms before price
Check mold ownership before price, because a mold that belongs to you may be used for your products only, while a mold whose ownership is unclear may be reused, shared, or withheld, and because a cheap price with unclear mold terms is a cheap price that costs your design's exclusivity, while a dearer price with clear mold terms protects it. Ask, in writing, before payment: who owns the mold, what it may be used for, where it is stored, who maintains it, what happens when production ends, and what happens if the relationship ends, because each answer changes what the mold ownership is worth, and because a mold term that is not written down, with its meaning, is not a term a buyer can rely on.
A buyer who checks price first and mold terms later will often discover, after paying, that the mold terms do not protect their design, and will face a choice between accepting the terms, renegotiating at a disadvantage, or abandoning the order, at cost, delay, and dispute. Check mold terms first, because mold terms protect the design itself, while price protects only the budget, and because a design unprotected is a design at risk, however cheap its production appears.
Check timeline realism, not speed
Check whether a supplier's timeline is realistic, not merely fast, because a timeline that promises prototype, mold, sample, and mass production faster than the work allows will slip, and because a slipped timeline delays the project, disappoints the customer, and disrupts the schedule, while a realistic timeline, even if longer, allows planning, and planning prevents disruption. Ask for the timeline in writing, with its start point, its end point, and its exclusions, because a timeline stated without them is a timeline that cannot be planned on, and because a supplier who states a timeline without its start and end is a supplier whose timeline cannot be checked.
Compare timelines across suppliers for the same design, at the same scale, in the same material, and in the same quantity, because timelines differ by design, and because a timeline that is fast for one design may be slow for another, while a timeline that is fast for all designs is a timeline that is likely unrealistic for most. A supplier whose timeline is realistic, stated with its start and end, and confirmed for your design, is a supplier whose timeline can be planned on, while a supplier whose timeline is merely fast, without its start and end, is a supplier whose timeline will slip.
Check communication, not just capability
Check how a supplier communicates, because a supplier who replies usefully, specifically, and promptly to an inquiry that names the design, the material, the scale, the quantity, and the market is a supplier who will communicate usefully during production, while a supplier who replies generally, vaguely, or late to a specific inquiry will communicate generally, vaguely, or late during production, when communication matters most. Write an inquiry from facts, and judge the reply by its specificity: does it confirm for your design, or does it merely describe its business in general, because a reply that confirms for your design is a reply that can be relied on, while a reply that describes generally is a reply that cannot.
A buyer who judges a supplier by its catalogue alone will miss its communication, and a buyer who judges it by its communication, through a factual inquiry, will learn how it will communicate during production, when prototypes need approval, when molds need correction, and when timelines need adjustment. Communication is not a soft criterion; it is the mechanism by which production problems are solved, and a supplier who communicates well will solve them, while a supplier who communicates poorly will let them grow, until they become failures.
Check the inquiry reply, line by line
Read a supplier's inquiry reply line by line, against your design's facts, before paying, because a reply that confirms the material, the scale, the quantity, the minimum, the timeline, the mold terms, the packaging, and the price terms, for your design, is a reply that can be relied on, while a reply that confirms some but not others leaves the unconfirmed terms to fail, however well the confirmed terms match. Check each term: does the material match your design, does the scale match your collection or display, does the minimum fit your quantity, does the timeline fit your schedule, do the mold terms protect your design, and do the price terms fit your budget, because a term that mismatches is an order that will fail, even where the other terms match.
Ask again, naming the mismatch, where a term mismatches, because a mismatch found before payment can be corrected, while a mismatch found after payment must be disputed, at cost, delay, and effort, and because a supplier who corrects a mismatch before payment is a supplier who will correct problems during production, while a supplier who dismisses a mismatch before payment will dismiss problems during production, when they matter more.
Do not choose on price alone
Do not choose a supplier on price alone, because the cheapest supplier who cannot produce your design at your scale, in your material, or in your quantity is the most expensive mistake, costing the order, the shipping, the delay, and the replacement, while a dearer supplier who can produce your design, and confirms for it, in writing, costs only itself. Price matters, but it matters after capability, mold terms, timeline, and communication, because a price for an order that cannot be produced is not a price at all, it is a number attached to a failure, and because a price for an order that can be produced, with clear terms, is a price that can be planned on.
Compare prices for the same design, at the same scale, in the same material, in the same quantity, with the same mold terms, and the same timeline, because prices for different designs, scales, materials, quantities, mold terms, or timelines are not comparable, and because a price that appears cheap for one set of terms may be dear for another. A buyer who compares like with like will choose the cheaper price for the same order, and a buyer who compares unlike with unlike will choose a price that does not correspond to their order, and will pay for the difference later, in correction, delay, or dispute.
What to confirm, before paying
Before payment, confirm the capability for your design, the material, the scale, the quantity, the minimum order with its unit, the timeline with its start and end, the mold terms with their meaning, the packaging options, the price terms, and the certificates that apply to your market, by name, with documents attached, in writing, for your design, not for model cars in general. Name the design, the material, the scale, the quantity, and the market, so the supplier can confirm for your design, and so the confirmation you receive is the confirmation you can rely on, and so the payment you make is a payment for an order that will serve.
A buyer who confirms capability, mold terms, timeline, communication, and price, in writing, before payment, has chosen a supplier on evidence, not on marketing, and has done the work that prevents the common failures: the incapable supplier, the unclear mold, the slipped timeline, the poor communication, and the incomparable price. A buyer who skips that work has saved an hour and risked an order, and the hour saved is rarely worth the order risked.