JulianS, Dutch, thank you very much. Haynes (God bless him) mentions that it is the shallow indentation, but when I postioned it in the box it did not look right. For some reason I got it into my head that the flat straight outside edge should be postioned top most horizontally. I know, I know, I should have checked before I removed it. I will put it all back together again and this time maybe it will function as BSA intended.
John