It is pretty close to the E3 which has a different trigger housing than the old M60 one. The triangular shaped piece for the trigger guard on the front and the "F" marking where it is if memory serves correctly seems to be for an E3 why I chose the E3 variant: I still work on the old M60s and knew it was not one of those but it seems to me that that particular housing is for an E3 or E4 (but I have not worked on one of those in a few years so I cannot remember fully).