Can anyone date my Webley Junior

[Sluggard]

Appealing to all you knowledgeable airgun collectors. Now well into my retirement I am finally finding time not only to renew my interest in airguns but also to give my small collection the care they deserve. Having just finished servicing my Webley Junior I am curious to determine its age, my guess is 1970's but confirmation would be appreciated.
S/N 436
'O' stamped behind trigger guard
'B' stamped on front of barrel hinge post
Bakelite handles
Smooth bore
Adjustable rear sight
Brown saddle and trigger guard.

Next project is the Webley Service which is in dire need of TLC. This is a new acquisition which I managed to salvage from being scrapped. I am really looking forward to dismantling and servicing this classic gun. I may need some help from you guys but will post later.
Thanks

[Garvin]

Welcome to the BBS buddy. I had a quick look at the Hiller book on air pistols but I couldn't see any mention of 'O' inspection marks. I think you'll find the 436 is a batch number not a serial number.

Good luck with the Service Mk2. There are some real Webley experts on here so you're in good hands if you need advice.

[Sluggard]

Thanks Pat. Thats all the information I need. There is no '4' after Birmingham so that dates it around the 60's. Thats terrific, a bit earlier than I thought.