Name the question.
Do you need to see the size in your hand, check an enclosure around a component, or explore how two parts meet? Explain that purpose with the model.
Mark the features that matter to the question. A critical mounting hole deserves a clear note; a surface included only to show the overall shape may have different requirements.
Keep a useful revision record.
Identify the model revision you are sending and describe what changed since the previous version. Keep related parts clearly named so the intended assembly is easy to understand.
For example, a revised enclosure lid could have a changed slot and an unchanged outer profile. Pointing out that difference is more useful than sending several similarly named files. This is a hypothetical brief, not a customer case study.
Choose the print around the purpose.
FDM and resin are available processes to discuss. Geometry, finish and use should guide the options in the quote; the word “prototype” does not select a material by itself.
A physical prototype can inform your next design decision. It does not automatically validate a final product or establish a performance certification.
Give each comparison a question.
If two versions are intended for comparison, name both revisions and state the difference you want to assess. For example, a short slot and a longer slot might explore an adjustment requirement. Keep the quantity for each version explicit, then identify which revision you want used for any later run.
The desktop-bracket study works through this fictional choice. Its illustrations are concepts; a real design would need dimensions, use conditions and suitable physical checks.