Thanks for prompting me
@Chadrinkincat; here is my one, for everyone's consideration.
Mine doesn't look like F1 to my untrained beginner eyes... Especially the line around the outside of the lid. But I defer to the opinions of others.
The only detailed source I've found on them so far, and with useful photos as well, is this:
http://www.jadepot.com.cn/bbs/forum.php ... tid=273732
If that article is correct (and if my poor attempts at translation haven't led me astray), it seems that mine is the #4 version in the description, and it seems that that version might not be an F1 pot (and if that's right, then presumably that means late 80s onwards).
I look forward to hearing from others around here (and seeing more photos if anyone else has got some). Thanks in advance for using up everyone's time, effort and knowledge for free.
(and before anyone asks, no, the inside isn't coated in shoe polish, it's just years of old puer... it was completely clean when I got it more than a decade ago)
Andrew