The link should work, although it's not a direct link. (forum's protection)
It seems that our 180 Summicrons are probably in the same batch. My SN is 3740800.
I recently picked up a 13338 as new-old stock in the original box from a Leica dealer for $125. You just have to keep looking and eventually something will turn up.
phuang3 wrote:
No. For 280/4 APO, you need 13338 which is even harder to get.
I will just use my Singh-Ray Lighter Brighter Warming Polarizer in the Cokin P Mount size (filter has sprockets to aid in rotating) and use it on my 280mm f4 Apo Telyt; it is now also available as a Neutral Polarizer as well: