Thanks for the info but the goal here is to find and document other 68/69 Camaro's with their original LH door mirror frame that has no mold line/seam.
Chick, I highly doubt you're going to find any.
There were three suppliers to Chevrolet for the outside rear view mirrors in the 1960's. Donnelly, Ajax and Standard. (Although I've never seen a Standard mirror on an original first generation Camaro. If you DO have a Standard mirror on your car, please contact me!!)
I've examined literally hundreds of these mirrors over the last 50 years and ALL Donnelly mirrors had the line, even on service replacement mirrors that were supplied well into the 1990's. Ajax mirrors even had the line, although not as pronounced as the Donnelly mirrors. I don't have enough pictures of a Standard mirror to tell, but from what I do have, it appears they don't have a parting line. But again, I've never seen a Standard mirror on a 67-69 Camaro.
Your theory about the chrome platter cleaning up the line is valid since I've seen that several times in the past. It's unfortunate, but unless you stipulate that the line needs to stay, they may not know any better.
Your only option now would be to get another original mirror and have him rechrome it, but this time make sure he doesn't remove the dumb line!!!
Ed