Crankshaft Main Bearing arrangement

ref: 1952 Tiger 100C
Hello again, I have now stripped my engine down. . I have a couple of questions concerning the main bearings and associated spacers etc.
. In my initial post, re the direction of the crankshaft nut thread I said that 45 or more years ago I modified the crankcase and fitted a Big Bearing Crank. The crankshaft I fitted has a part number E3296, I’ve no idea what engine it came from but it worked fine. My questions relate to the crankshaft & main bearings.
1. Has anyone any idea which engine the crankshaft is from?
2. The timing side bearing has pressed steel shields on both sides. The outside one is a press fit in the crankcase and the inside one is held in place along with the bearing with a circlip. In addition there is a spacer which is 11/2” dia & 0.125 thick, recessed on the outside side, between the timing pinion and the bearing and another spacer between the inside of the bearing and the flywheel
I have (I hope) attached a photo of the parts I’m referring to in the order which they were assembled.
My problem is that I can only find reference to the spacer (which is called a Clamping Washer in the parts lists) between the pinion and the bearing, no reference to the shield circlip or the second spacer at all.
As the main bearings appear to be lubricated by splashing I can’t see the logic of the inner shield.
Has anyone got any thoughts please.
Thank you regards
Pete