Jim..... Could be another Unicorn Part, Heard Of But Never Seen. There are rumours of a One Piece Big Journal Crank, which precedes the more familiar three radial bolt type. I would consider it impossible to manufacture and machine this design of crank from a single forging, so on initial examination it may appear to be in one piece, because of the hidden bolts and hence the myth that is made in one piece.
As long as the journal sizes are within the accepted dimensions, and the throw is correct, then it should fit fine. Do not neglect the usual cleaning procedure for the oilways.
No doubt the respected contributor JulianS will be along soon to offer further enlightenment.
Good thought there berger, another possible explanation.
Swarfy.