To revive an old thread, does anyone know about the numbering on the early SERE 3003's?

I have #410.

#502 is for sale on ebay right now. I've found references to #587 and found a photo online of #154 - but that's all!

The guy who is selling #502 says he thinks there were 600 early SERE's with serial numbers - but does anyone know?

Thanks
James