Anyone know anything about this dress?

Hello! I've had this dress for a while and have always thought it an interesting piece. My guess was that it dates 60s because of the length, the center back zipper and overall style. The only label is a very faded white square that states "Lot Sz 13." The dress itself is definitely a S/M when worn. The metal zipper says "TRIUMPH" I believe and it looks like originally it was painted an olive green that has worn away.

When I first acquired it, the brown was a darker shade, however I had to clean it, as the fabric was sticky to the touch all over and smelled like death, so the dye bled some and led to this light olive/brown color. (Those were my early days. I might have chosen not to clean it now or at least not soak it....)

If anyone has any info, I'd love to know about it! Thanks!

 

Thanks!