I tried searching to no avail, and the guys over at UZI talk sent me back here for advice.

Does anyone know which (if any) uzi magazines can be readily identified as having been manufactured prior to sept 14th 1994?

I'm in NYS and still have to deal with the AWB. I have a line on some German magazines at a good price, but from everything I can find- Germany issued UZIs to tank crews past 1994, so unless there are some markings on the mags I can track down, I don't think the seller will ship to NYS.

Conversely, does anyone know a NYS supplier for mags at a reasonable price?

In most respects, there is no such thing as Pre-Ban / Post-Ban Uzi mags..

Use them, or somebody else will.  

If you can find chinese mags imported with the Norinco 320's you should be GTG. They have a small 5 pointed star to identify them at the base of the mag, in the back. All things chinese were banned from import prior to the '94 AWB.

Try RTG Parts for  preban uzi magazines.

http://www.robertrtg.com/uzimags.html

"Original Israeli IMI production 32rd magazines produced for the German army. Conditions range from very good to like new. These are the best Uzi mags available. For those living in Ban-States; all of these mags are Pre-Ban being produced prior to 1994. Stock up while the prices are low."

Israel used a small, 5-pointed star to mark military contract purchase (IMI and imported) Uzi magazines.  Don't depend on that star to say anything about who made the magazine.

Check out Uzi Talk's Magazine Reference Page for details.  According to that page, Chinese mags will say "Made in China."  And I'm not 100% certain "all things Chinese" were banned in the import ban, either.

I stand corrected.