What type of crank is this?

[mark]

Have just dismantled my spare engine to check it out. Engine No is 1957 Road Rocket. The crank is quite different to the one I am using in my 55 rocket which is the 3 bolt. This one has no visible bolts. Where each of the 3 bolts should be are 3 small countersunk indents and it appears to have been ground back. The central web is almost the full width of the flywheel for the entire diameter where the other one varies in thickness. So it seems to be a lot heavier but I havent weighed it yet. It is stamped 5872 and is the large journal. It doesn't match the description of any crank in my reference material. Anyone shed any light on this?
Regards
Mark

[trevinoz]

Mark,
         there have been a few inquiries about these cranks. They were fitted to the Road Rocket in at least 1956-7.
There is a bit of conjecture as to whether they were fitted prior to 1956.
In 1958 the radial bolted crank was fitted to all A10s.
Trev.