Many minor mechanical differences separate the various Vulcan variants, but these were basically variations on the same theme. The more noticeable cosmetic differences however are as follows, inc. info on the Xocet and Stingray (Brum built ones that is), which were basically continuations on the Vulcan theme ...

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Vulcan MkI: thinner barrel and slimmer stock than later models.

Vulcan MkII: fatter lacquered stock with pistol grip cup with white spacer, and a white butt pad spacer, too. The MkII also had/has a thicker 16mm barrel, and different front sights.

Vulcan MkIII: early MkIIIs sported same style stocks as described for the MkII, but later ones had plain pistol grip ends and no white spacers. These had the same style sights and barrel as the MkII, although later carbine K versions had threaded muzzle-breaks fitted which incorporated the front sight.

Xocet: a no thrills variant of the Vulcan (no safety and very plain stocks) with re-jigged breech so no gap apparent from above when rear sight removed.

Stingray: mechanically the same as the Vulcan but with finger grip flutes running length of stock, re-jigged breech so no gap apparent from above when rear sight removed, and a threaded muzzle break as standard incorporating a front sight.

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The Webley & Scott Vulcan air rifle first hit the market in 1979. All Vulcans were available in .177 and in .22. With the exception of the Xocet, all of the above have also been available as Walnut Deluxe Specials, too, and all models except the MkI have been available as carbines. At one stage I had eight examples of Vulcan in my collection, but now I only have the one: a MkI .22 SE special, which is one of only 110 of these ever made, ergo very rare and extremely collectable (have written a brief history of this particular model at the end here, as below).

Am a big fan of the Vulcan as you can probably tell, as imho, notwithstanding the use of a roll pin at the breech pivot instead of a breech bolt so as to save production pennies (why oh why did Webley do that ???), the Vulcan, particularly the Mk.I, was a real land mark air rifle, not only for Webley & Scott, but for the British air gun industry as a whole, as straight from the box, the Vulcan could muster upwards of 11ft.lb unfettled.

The Vulcan “One of 110” Walnut Special Edition (SE)
During the launch of the Webley & Scott Vulcan (first models weren't referred to as the MkI until the MkII went into production three years later), the factory produced 110 Special Edition versions wearing high-grade walnut stocks, and with gold plated trigger and safety catch levers.

So as not to be confused with the other walnut versions of the Vulcan that Webley were also to produce as an up-market mass produced up-grade item at that time (called the Deluxe throughout the Vulcan run) , these Special Edition Vulcans (oft referred to as The Vulcan SE), were given a fresh serial number range starting with a nine (9).

So if you are shown an alleged Vulcan SE check the serial number, because if it doesn't start with a nine (9), it is not one of the 110 that Webley & Scott produced, merely a doppelgänger, most likely cobbled together around one of the aforementioned Deluxe (lower grade walnut) Vulcan variants?

The 'Special Edition' (SE) one of 110 variants as detailed were limited to what we now know as the series one Vulcan. Some people incorrectly think that there may have been more than 110 of these, however. Here is how this confusion has crept in:

As stated, each version of the Vulcan (I, II, and III) came with a walnut stocked Deluxe version. They also all came as a Customwalnut version, too ...

From the Series II Vulcan onwards, the aforementioned Custom Versions were called the 'Special Export' model. This inevitably got abbreviated by the trade to SE.

This is where the confusion comes in, as the ORIGINAL Vulcan SE was the Special Edition model, and as stated, all Special Edition examples have their own specific serial number range starting with a nine (9). As stated, there were only ever 110 of these manufactured.

All the Vulcan Special Export variants have serial numbers which slot straight in to the running sequence of serial numbers, however, and run into their thousands.

Poignant Foot Note
Webley & Scott air rifles using the model names of Xocet and Stingray were also made and marketed after the original British Brum based manufacturing company of Webley & Scott closed in 2006. They were sold by the outfit that bought the Webley and Scott name. These later examples were made in Turkey and/or Eastern Europe, and imho leave a lot to be desired. Hope this all helps: G.