The 2TG series of engine had alot of minor changes as they got newer. I'll try get pics of the changing rocker covers and post em up.
The First 2TG (11111-88220) Had "Toyota" and "1600" on the rocker cover.
(pictured further down this thread)
The 11111-88222 Rocker cover did not have "1600" on it. It had its EGR valve mounted there so only had "Toyota" on the Left Hand Side.
The 88260 Head appears to have received two styles of Rocker cover. The 88222 Version and the one used for the 88261.
The 2TGEU 11111-88260 and 11111-88261 heads Had "Toyota DOHC" on them and the DOHC lettering had raised edges.