Our pool pump uses an Intermatic timer which stopped working a few weeks ago. The mechanical timer mechanism is labelled as a Paragon Electric 4004-71M. After scouring eBay for a few weeks with no 4004-71M timers appearig but several 4004-71 models... I bought one, hoping it would fit.
It looks almost identical and mechanically does fit into the housing, with mounting tabs in the right place. However the original 4004-71M has a through hole at the bottom where a mounting screw secures it to the metal box. The 4004-71 has a smaller diameter hole which doesn't go all the way through, intended only to hold a cover over the wiring.
As my father would surely have said in this situation: "You can have a through hole anywhere, if you want it badly enough."
The timer chassis is bakelite, which drills cleanly if one takes it slowly. A few minutes drilling resulted in a hole suitable to mount the 4004-71 into the housing which originally held the 4004-71M.
Adding to the amassed knowledge of the Internet: the 4004-71 is not a direct replacement for the 4004-71M, but can be modified to work.