You have a nice example of a second [post-War] series Webley junior air pistol. The 1st series [Pre-war] Junior models had wood grips, and an adjustable rear sight. The 2nd series was equipped with stamped steel "tinplate" grips, and the adjustable rear sight was eliminated. Pre-war serial numbers were sequential, and prefixed with the letter "J". Barrels were smoothbore.
The early post-war Junior had a redesigned grip frame, with vulcanite (plastic) grip panels, and retained the non-adjustable rear sight. This is yours. On later versions of the post-war Junior, the adjustable rear sight was reinstated. Another variation seen within this series was a change in the grip panels, with a forward extension at the top of about 0.250", as seen in the graphic on the box lid shown. Variants with black lacquered frames can also be found within this series. A rifled barrel was available as an option. Sequential serial numbers were replaced with a simplified batch number which simply indicated the production lot.
The final iteration of the Junior saw some major changes. A slightly bulkier aluminum frame, a sturrup style barrel catch, epoxy paint finish, and a rifled barrel as standard equipment. The adjustable rear sight was retained. The Junior Mark II was superceded by the Webley Typhoon - a youth oriented version of the Hurricane.
Values here in yUK depend on condition -as ever - an whether nor not you have the box and instructions. Never having seen one in Canada, and with a profound igerence of vintage air-gun prices, I'd be lying if I told you how much I thought it was worth. Here a MIB example sells for around £150 or thereabouts. Not rare - my next-door neighbour has one just like yours for less than £100. Every spare part is still available, BTW.
tac