Sorting out some very old ICs, I came across this date code series.
These are all MC899P, MRTL (Medium power Resistor Transistor Logic, MC700/800 series) from the late 1960s through 70s. It's a "dual buffer."
In the photo the left hand pair are the earliest - they have the 4 bumps on the package underside, that rapidly went out of style. The next pair's date code is 7204 ie 4th week of 1972. The right hand pair are 7725, 25th week of 1977.
But what does "905" mean? Is it a date code or something else?
Oh, and those were the days when ICs might be supplied in little styrofoam boxes. Before static electricity was invented.