Schema error - no global identifier for handmade product

[Lorel]

I'm trying to set up Schema for a client who manufactures his own products in a small cart. The schema got a warning about no GTIN, MPN, ISPN. However, i the product doesn't have a GTIN, MPN, or ISBN number. Only the name of the product in words, i.e., "part-name". From research, it appears I should include it as a MPN. Is it ok to use the part name instead of part number?

[JesterMagic]

Are you using the Google Structured Data Testing Tool?

I wish Google would make it more clear when you use the tool, that it is just testing for the rules Google uses to display rich snippets. Products Structured Data does not require those items by schema.org. Only Google does for displaying the product using a rich snippet in the search results. All those warnings and errors make web masters think they have made mistakes with the actual schema.

Googles requirements for rich snippets for products with reviews is pretty limited. You can try to fudge things a little bit but it has been reported that Google will remove the rich snippets if they think you are taking advantage of things.

Not that I think it will likely happen. My competition uses a wide variation of structured data for products and reviews with a lot of it not really following the guidelines (especially the item type) and they still have rich snippets showing