I have just been looking at the picture of the GAMO Target in the 4th Edition of "The Airgun Book" on page 75.

This particular pistol does not have the same rear sight as mine - but one that is listed on the Chambers spares as an "Upgrade Rear Sight".

However, the cylinder also looks longer and has some extra holes in it at the rear to accomodate this bigger rear sight that looks a bit like the rear sight from an Original Model 10.

I am guessing there must have been two variants of the GAMO Target - mine shares the same cylinder and rear sight ( but with modified metal adjuster screws) as the Centre, but this other version can be seen on the Chambers drawings to have the longer cylinder fitted with a short rear plug (spring guide) to accomodate this different rear sight assembly (that sells for less than the standard rear sight).

Anbody know any more about the Mk 2 Target ?