The middle piece between the two black pieces around the edge of my original 1946 mirror are "sagging" (popped out). I thought about using JB Weld or something similar to adhere it back in the groove, but I'm not sure what either (79 year old) material is. Has anyone successfully reattached theirs?
Maria - Not sure what that mirror came out of, but sorry to say it's not original (factory equipment) to your truck. Art Deco trucks (1941-46) did not come equipped with inside rearview mirrors, only the exterior mounted ones. Passenger cars did, but they didn't look like the one you have.
That point is neither here nor there though as it's currently in your truck and sounds like you want to keep it. With that in mind, you might try some weather strip adhesive applied with a tooth pick. Once you dab some into the channel where that bead rests, use a bunch of wide flat rubber bands to pull it into the groove and hold it in place while the adhesive cures. You might have to gently pry open that groove where the bead rests to get the adhesive down into the bottom of the channel. Let us know how it turns out.
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
Gdads, thank you! I'll have to get. Some of that. I Googled previously and it said; "Yes, some WWII military trucks did have interior rearview mirrors, but not all." That, coupled with the fact that it had two perfectly drilled holes and the removal was as difficult (as if it had been on for 80+ years), led me to believe that it was original. It's definitely period and, considering it was used as a farm truck in it's past life, there were no frivolous additions after purchase. All we've found are a few "redneck ingenuity pieces. Haha
1946 Chevy Getting started on Bruno Follow the story in the DITY Gallery You can't buy happiness but you can buy a truck ... and that's pretty much the same thing.
Maria - The vast majority of our trucks have a PO (Previous Owner) addition or modification of some sort - LOL! I should know as my '51 has so many (I'm still finding them after all the years I've had it) of my Grandpa's "modifications" and "improvements". Those kept the truck running and useful to him over the decade before the truck became mine. The inside rearview mirror that came with the truck when I got it turned out to have been from a 1962 Cadillac. I think he used it first because it was what he could find for cheap but it also provided a wider rear view than the stock mirror and it had the little flip lever to stop getting blinded by lights from behind at night.
Nope, no "frivolous" additions. Just things that either kept it running, reliable or provided something he needed or wanted. I plan on keeping the vast majority of them just like he put them in.
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
Gdads, I'm happy to report that the adhesive worked! Thanks again for the help.
1946 Chevy Getting started on Bruno Follow the story in the DITY Gallery You can't buy happiness but you can buy a truck ... and that's pretty much the same thing.
Glad to hear it was a success!!! On to the next fix.
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
as it's currently in your truck and sounds like you want to keep it. With that in mind, you might try some weather strip adhesive applied with a tooth pick. Once you dab some into the channel where that bead rests, use a bunch of wide flat rubber bands to pull it into the groove and hold it in place while the adhesive cures. You might have to gently pry open that groove where the bead rests to get the adhesive down into the bottom of the channel. Let us know how it turns out. 
I should know as my '51 has so many (I'm still finding them after all the years I've had it) of my Grandpa's "modifications" and "improvements". Those kept the truck running and useful to him over the decade before the truck became mine. The inside rearview mirror that came with the truck when I got it turned out to have been from a 1962 Cadillac. I think he used it first because it was what he could find for cheap but it also provided a wider rear view than the stock mirror and it had the little flip lever to stop getting blinded by lights from behind at night.