This unusual but distinctive looking plate/washer, was fitted on the Timing side of the Lucas MagDyno magneto platform bolt on all OHV and Side Valve models - and helped ensure that when the magneto bolt was fully tightened in the 'slotted' engine plate, it spread the load, to help prevent the magneto slipping and mag chain tension being lost.
Price is each.
As can be seen in the accompanyning photographs, an original (alloy) Norton OHV/SV MagDyno platform is shown, as well as the original Magneto platform engine bolt and A2/118 Locking plate, and washer/nut. The Timing side rear engine plate on OHV and SV models had similar positioned slots in them - so the alloy platform could be slid either forwards or backwards on top of the rear engine plates, to correctly set the magneto chain platform.
However, as can be seen from the original locking plate in the photograph - these plates would eventually get 'chewed' and mis-shaped, the result being that it seemed more difficult to fully tighten and lock the magneto in position. I myself found on OHV/SV models I owned, it was not unusual that once the main bolt was fully tightened, the magneto tension seemed to have slipped again!
Therefore, replacing the orgiinal chewed washer with this new item . . . although may not fully cure the issue of the MagDyno 'shifting' slightly when tightening this bolt (it did seem to be more of a design issue with these models), it will at least give the best possible chance of spreading thge load evenly as the bolt is fully tighened, over a wide as area as possible - which I think was its original purpose. As with the original plate, their is also a second hole, which was for the smaller locking bolt that screwed into the bottom part of the alloy casting, and was tightened once the engine bolt was fully tightened.
We have this item lasercut in the same gauge steel and profile as the original Norton item, before linishing the edge and then having it dull nickel plated, as the original Norton item would have been. As an aside - although not immediately visible to onlookers - this item will make that engine plate area look much smarrter, for those giving your bike close scrutiny!