Rear plate does have a 12mm or so hole in each 1, have looked on the oldskool site & they have a stock 74, 76 Falta & 75 Falta sitting together & it looks closest to the 76 Falta, interestingly the 75 Falta has the mounts a lot closer to the pivot
This is the arm I've been given to use, was thought to be a 74 & it was used in another bike a couple of seasons ago with no problems as far as eligibility