What's the diff between a "Rev. A" and a "Rev. 1"?

Hey guys, trying to make heads or tails of some tech documentation I picked up from various Google sources. I have a feeling one "rev" is for internal use, but not sure which one. Anybody here familiar with this convention?

At my work, revision level 1 indicates it is still in prototype stage and revision level A indicates it has been released to production.

Where I used to work, it was just the opposite--letter revisions indicated prototypes and numbers were for released parts. It's just whatever system the quality department decides to use.

And one place where I used to work... 1=prototype, A1=pre-production, A=production...

And I, as a design engineer had to re-release my otherwise unchanging documentation 2 more times for production release (and it was three different databases)--I hated it and when I had the chance to change the system (a new company), the rev. did not change between engineering and production (on one database)--I just had a data base field that had the release level... Saved about 1/2 of the time (or more) of engineers playing "documentation roulette" to release a product.

Then there was marketing--Our major software releases were going from 7.x.y to 8.x.y to 9.x.y--Marketing thought it was changing to too large of number, so they started over at 1.x.y again--massive confusion and new customers wondering if this ("old" company in the field) was releasing "bug 1.x.y" software...

-Bill

-Bill