looks like they used abit of glass filler like mar glass then a body filler looks to be 1/4 .here is the deal the fender is over 70 years old hard to say whats going on need to strip it to steel were hurt and i would NOT strip the hole fender less its failing .you may get in to alot of work and time .less the insurance gives you a open check? i been there and dance with the insurance were you can put 20+ hours of body work in the fender with no paint time. i do know over the years the lips get bent and rip getting them to look good takes time if you do not want much filler. but i have and would put a thin coat over a body panle many times then 6 coats of primer and a skin coat of putty or the primer them more primer