I was informed that Carlisle photocells used to be calibrated to switch on at 55 Lux, then they changed to 70lux. In the early 2000s the Lux level went back to 55 and now it's at 35 Lux! I recall that whilst PECs were available in a variety of standard switching ratios, in the 1990s when I was really into collecting streetlighting, it seemed that every thermal PEC was 70 lux, presumably because the majority of lighting was still SOX and demanded a longer run-up time.
The NEMA sockets from this period continued to have a datum mark and the word "NORTH" stamped on the top stemming from the earlier requirement to have correct cell orientation in relation to the lantern, especially when used in retro-fit installations to replace the original timeswitches.
Presumably in those early days, operatives would also be trained to re-orientate the socket on brand new NEMA lanterns once they were mounted on the column.
I think later cells didn't require any sort of setting, i.e the old Zodions with their opal, conical tops and universal LDRs.
On a current streetscene, it does seem that cells switch later than they used to do - in fact I think they switch off sooner too. A couple of local authorities in my area seem to be trialing a replacement for the SS5 electronic PEC. Rather than switch on at dusk and stay on, the cells seem to go "on-off-on-off" with the off period getting progressively shorter as the target Lux level is reached. Switching off in the morning is in the same manner, with the interval "on" decreasing as target Lux level is reached. It might be a faulty batch or a similar reason, but it can't be doing the lamps any good.