Should I stamp my jewellery models with my name.

Of course you have every right to put a stamp on your model but IMHO it may deter buyers.
Is your name / logo / brand well known that it will be recognized by final user? Probably not. Even the final user might see that stamp as something confusing and unnecessary.
It would make sense to put a stamp on product that is completely designed and produced and sold by you as final product.
You should find satisfaction in royalties which you get with every item sold so be sure to have "editorial" or "custom" license on your models.

On your models (if design is completely developed by you and doesn't resemble for example anything from Cartier collection) you can make engraving in any place. This can be seen simply as part of the design.

thank you both

nic