[Lynn Eades]

Kevin, here's how I see it:
The wheels with ball bearings fitted all have their centres finished the same
1.There is the bronze solid bearing.
2.There are the early semi thrust bearings (bronze cage and stripable) Yes, these have a different spacer than,
3.The 6408 (previously 1408)metric series annular grooved standard ball bearing, which are found in both British and Canadian wheels with a common width spacer.
Let me know if I have this wrong.

Just to complicate the above is the early and late style seal arrangement.