This model was manufactured from the late 40's up to the late 60's. I suggest you contact Webley at the link below for more information.
A Webley & Scott Junior is worth: 100%=$150, 90%=$110, 60%=$80 Mfg late 1940s to late 1960s.
Webley Mark 1 pistol (original. There are several variations) 1924-31. Webley Mark 1 New model 1935-64 Webley Mark 1 Rifle 1926-29
Take it to a professional.
which model I, II or III
I am a little confused by your question. Do you mean Webley air rifle. I know that Wembly makes scopes but I am unaware that they make air rifles. If you mean Webley then I need to know the condition and the model of the rifle to give an estimate of value.
50-200 USD
To get an estimate of value you will have to state the condition of the rifle and give the SN#. There are 5 different series of this rifle.
The Jaguar by Webley & Scott was made between 1940 to late 1970 and again in 2008 to now. It came in .177 or .22 Caliber. Some parts were interchangeable with the Webley Junior and Diana .22 air rifles. Unfortunately you did not state state the current condition of the rifle so no estimate of value can be given. Price is determined by the current working condition. Poor, Fair, Good, Very Good or Excellent (like New).
The Webley $ Scott Hawk MK2 was made between 1974-77 it had an optional .22 barrel. Please state the condition of the rifle to get an estimate of value. Is it still working? Is it in Poor, Fair, Good, Very good, or Excellent condition?
Not a serial number if that is on a Sears or JC Higgins rifle. Might be a serial number on an Ithaca rifle. Please list all the markings on the rifle, just as they are on the rifle. sales@countrygunsmith.net
See the link below for a list of places that may be able to help you.