Cooper actually used the Electromark tag from the factory for a short while. I think cooper may pay Electromark to take their name off the tag because the current cooper NEMA tags look just like the Electromark ones.

This is likely one of the last of the Crouse-Hinds OVZs before the redesign. I saw a Crouse OVM with the Electromark Tag on it.

These are cooper aren't they? Only the L-150 and L-250 were CH designs

No the so-called "L150 and L250" are actually Westinghouse design OV15 and OV25 (for the record, I will always designate these as either 4th generation Westinghouse or Crouse-Hinds OV15 and OV25 because that is the catalog designation). This is a Crouse-Hinds design because this was in production along with the Crouse-Hinds OVM and OVL. The Cooper version came out in the mid-1990s (around 1993 or 1994).

So how did the L-150 and L-250 designations pop up? If it was never used, how come those model numbers were made up?

I don't know. But I did have a Crouse-Hinds catalog from that era and they did retain the Westinghouse model designations as they owned the production rights as well.

Maybe they changed to the L- designations after your catalog was printed. I know there are a lot of false model numbers floating around here.

No, the catalog was from 1985 and I got the updated Crouse-Hinds catalog featuring the OVS, OVM, and OVL,which was printed in 1986. Besides, I had a box that a Niagara Mohawk crew gave me when they were relighting Cumberland Ave from Series Incandescent to 100 watt HPS and they were using Crouse-Hinds OV-15s. This was in 1985.