I have a Webley Vulcan 177 from about 1979. Birmingham marked, beech stock, no grip plate, no white buttplate spacer, pencil bbl, but ser# 907890. Is this a Special Export? How about that ser# that starts with 9?
Sounds like a mk1. Good gun when the trigger is sorted. Start by backing the spring screw out. It’s up top by the rear of the dovetails. Make sure it won’t bump fire. Should become a decent sporting trigger. I don’t know anything about the serial #.
Here is my Webley Vulcan. I purchased it brand new from a dealer in 1983. I refinished the stock when I was a kid. I’m not sure if I added the white spacers. Too long ago and too many concussions. Great gun. Likes a slew of different pellets. Hope these pictures help.
That one I believe is a mk2. If it has a fake 2 stage trigger it's a mk3 (just a spring loaded hinge in the trigger. Not true 2 stage) I have a mint mk3 I bought several years ago off a gentleman from NJ. Real good sporting rifle although I never shoot it. Beeman offered a deluxe checkered walnut stock that was very nice. I wish I had that stock.