Hello, I am working on my philco 38-4 chassis and noticed it looked like there was something riveted to the chassis top of the 6k5 where the rivets go. One rivet is still there and the other one is now a screw(appearently added). The rivet has what looks like a whats left of a tube shield holder piece of metal underneath it, kinda like somebody tore it off instead of just removing the rivet.

Sean,
Probably. When you finally fire the radio back up, if it howls, screams, etc., then the shield is needed. Lots of the old radios somewhere along the line got re-tubed by someone who instead put in a "modern" metal version of the original glass tube, and for some reason ripped off the shield base. The case is the shield on the metal tube, and usually works fine as long as the case is grounded when you plug it into the socket. You would have to look it up, but I am pretty sure this was done by grounding pin one. I have worked on Philcos where the metal tube was not a viable option as Philco saved money by using tube sockets with no pin 1 you could solder to ground! Changing the socket couldn't be done easily either since the thing was deep, deep inside. In those cases I went with a snug fitting shield for a glass tube,and soldered a bent up piece of metal to one of the socket rivets, so that it would snug up to the shield when put in place.
Jim