How do you manage the versions of drawings that you send to machine shops for quoting?  I might send 2-5 drawings to a shop before finalizing the design, so I have all these 'revisions' (that aren't true Revisions since the part is not issued yet) and I end up adding a "v2" or "v3" etc to the end of the PDF filename.  And I want to make it really obvious so that when we place the order, the shop does not make me a part from the wrong drawing.

The way I do this now is I write "not for production" in all capital letters on the drawing and then I don't remove that until we have the finalized part.

In some firms they will use revisions A,B,C etc for pre-release.  Then the first 'real' release of the part is rev 0, and subsequent revs go 1,2,3...

Curious to know how other people handle this.