Elton,
I think that is called a dent. I suspect the bed apron may have impinged on the cab corner, possibly when the frame was flexing or happened when removing the bed, etc.My '42 does not have anything like that.

Kent



1937 Chevy 1/2 ton
1942 Chevy 1/2 ton
1947 Diamond T Model 509
1951 Chevy 1/2 ton
1950 Chevy COE Model 5700 ~ "Barney" ~ And more pix