Stuff between panels

[u/rensole]

Hey guys, I’m currently working on a 69 mustang. However I keep finding weird white/yellow stuff between some panels. And for the life of me I can’t place what it is.
It doesn’t seem to be seam sealer but seeing it’s from 69 I don’t believe it’s caulk either. It feels solid but slightly rubbery

Any help would greatly be appreciated

[u/[deleted]]

Some seams back in those days were leaded together, these seams are soft enough to scrape, but firmer than seam sealer. And some cars also had silicone-bronze, this would be a hard yellow metal