Ron,
I am attaching two screenshots. The first is an Ai version #240xxx, the second an AiS with #244231.
Given the difference of SN bigger than 4000 it seems unlikely thez came from the same batch. I would also agree with Pluton's statement that these lenses are not "original"
Thanks for that Wally.
Well spotted!
It certainly is a coincidence that both have appeared on eBay at the same time. It might suggest that there may be more out there??
I've asked the seller of #240XXX for the full serial number.
As to the reasons why; the only things I can think of are;
*The factory hasn't anodized /painted the original aluminium retaining ring
*Someone has deliberately removed the black finish
*The ring needed replacing and, with no new parts available, new items have been reverse-engineered from original and the part re-manufactured. Once the machine is programmed, it would take a modern CNC Turning Centre no more than 20-30 minutes to turn-up one of those parts.
Below are an assembly view and a couple of section views.
As you can see; the ring, part #40 (highlighted in red), retains the entire front group-assembly. With the correct tool; it would be quite easy to remove the ring, by simply unscrewing it.