This is the very important twin row, self centering bearing that was originally fitted in both top and bottom bevel housings in all International and early Manx engines (SOHC and earlier DOHC engines).
They are self centering, because they allow for the vertical shaft to be moved off centre slightly, and therefore it facilitates the cambox being 'swivelled' out from under the top frame tube, when working on the engine. It also allows for any small discrepancy in the cambox being out of line with the bottom bearing housing.
Update March 2020: As I am sure most owners of SOHC Norton engines know - these bearings have been obsolete for many years now, and we have been relying on sourcing old stock at very high prices.
We sold the last of our current stock in January 2020 and have not been able to source any more since. However, I have just managed to obtain a small batch of RHP bearings from the one supplier in the country who holds some - but they know how rare they are and therefore the price is very high - I am sorry this is the case, but there are no alternatives.
25/3/20 these bearings have now arrived and for the moment are back in stock - and are the genuine RHP article see photo. I know they are expensive, but I can only tell you that once these have ran out there will be no easy alternatives - I do not see them ever being made again by one of top quality bearing manufacturers
Note: these bearings were originallly supplied in greaseproof paper in 'rolls of 5' - see the photograph of a previous batch we supplied, which were supplied to me in that way, in the old 1970's yellow RHP box, which we then split up. This latest 2020 batch have been supplied pre-split into individual boxes - this is quite normal for UK bearing suppliers, rest assured they are the genuine article!
Additional Information on SOHC (and early DOHC) Bevel Bearings:
Because they have not been available for many years, whatever stock is still out there is very expensive to obtain - the bearing suppliers know this! So worth noting - for the top bevel housing, it is possible to use a single row 'none self centering' replacement of the same dimensions, which I can sometimes also supply (see Item 0006), however, it is really important that the correct twin row bearing is used on at least the bottom housing . . . failure to do this could mean you canot remove the cambox with the engine fitted in the frame! And if you can afford it, it is best to go for this bearing top and bottom. You must accept though that if fitting a (cheaper) single row, non self-centering 0006 bearing in the top - movement off verticle of the cambox when removing from a frame may be slightly more restricted. Both do the same job once in place though.
Final hint on fitting these bearings (because at the cost of them you dont want to waste them!!): I have fitted these bearings into housings many times over the years and I have found it is very important not to knock the inner bearing, or accidentally press it excessively, so that the inner race pushes 'out of centre' to the point where the balls totally lose touch with the outer race. Although the inner race will allow this . . . even with a brand new bearing, it is possible when pressing the inner race back into line that one of the small balls could be pushed out of its bronze cage - and be very difficult to get back in place, particularly if the bearing is now mounted in the bevel housing with no access to the underside. Therefore the message is - handle with great care! It is also very important to fit the dished washer (Item No. 0007) under the lower bearing - which was designed specifically to capture any errant balls that do drop, so as to avoid them dropping into the bevel box and crunching the gears. My old mentor Titch Allen told me that this design and bearing kept Norton's Service Department in business for many years!. Finally, whenever stripping the engine down, it is always worth checking this area (and bevel box) to make sure no loose balls have made their way out. The best advice I can give is - always handle with care and never take them off centre any more than absolutely necessary!