I really do not think this relay changed design for 1987.
My best guess is that it changed to 10 pins to support some later application, and they have gone to producing just one relay that supports both the old and the new. You just happen to have a newer one installed.
One of my favorite vendors has pictures of just the pin side (so I can't see the part numbers), but the Rebuilt relays listed for the 1987 model have 9 pins, and the New relays have 10 pins.
I do not know what 87H does, but I bet you do not need it.
1986 300E 5-Speed 240k mi.