Here is a good image of the/a
one piece crank [1].

I have a couple of such from Japan and Taiwan
and they seem to be 100% interchangeable down to
the last washer.

What I can see they are also identical to the
one depicted, only sometimes there is a big
washer/spacer between the chainring/sprocket
and the stationary cone, and they have a large
dustshield between the adjusting cone and
the lockwasher.

The locknut is sometimes 31mm which is a rare
combination spanner size. More often they are
32mm tho.

[1] http://user.it.uu.se/~embe8573/bike/1p-crank.jpg

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