Seam sealer?

[SlinktRR]

Can anyone ID what this is and what the best way to tackle it is? Maybe ancient seam sealer or bondo but I am not sure. It is dry and cracked and has started to warp the paint at the rear quarter/hardtop seam.

 

[PurpleBeeper]

Bondo (polyester) will be 100% brittle & should crack extremely easily. Seam Sealer (usually polyurethane) should have at least "some" flexibility left to it. Either way, you can scrape/chisel off what you can & paint stripper containing methylene chloride will take off either (and your paint too). FYI - Do not use methylene chloride in a closed garage

 

[Cmmopar]

Best way to fix that is with 30/70 Auto Body Solder.