Based on the serial number, it should be a 1979 model. The rear derailleur is an obvious replacement for the original 600EX. It is almost certainly a Shogun 1000 given the 600EX components. Shogun literature typically did not supply info as to the manufacturer of the frame tubing. Given the level of components is should be CrMo and most liked butted. The diameter of the seat post would aid in confirming this. Remove the post and there there should be a stamping below the insertion mark. It should be somewhere in the 26.3 to 26.8 range.

BTW, drive side pics are preferred, as this allows us to see the crankset and derailleurs, which are valuble. aids in determing year, level, value, etc.