Cam's Martini-Henry - PICS
Here are the two images Cam e-mailed to me of his early-dated MkIV Martini-Henry rifle -
First, the receiver markings on Cam's rifle - definitely a Mark IV, and definitely dated 1887.
This second photo clearly shows the underside of the wrist area of the buttstock, with plugged recess for the short lever and recess/receptacle in place for MkIV long lever. But for the additional info Cam has supplied, one's first impression would be that this buttstock was a replacement at some time in the rifle's life, using an earlier MK/II/III buttstock.
However, Cam also indicates that the buttstock markings are definitely those for a MkIV - without any evidence of earlier markings, I gather. Considering the early date (1887), this would be strong evidence that his rifle was one of the earliest of the Mk IV's produced - when the new pattern rifle went into production, Royal Manufactory Enfield would have had preshaped (but not yet marked) buttstocks of the earlier pattern on hand, with the recess already cut for the shorter lever, and simply used them up for Mk IV rifles by plugging that recess and cutting a new one to accomodate the longer lever. (The Mark IV rifle was not officially approved by publication in the War Dept.
"List of Changes" until 15 September 1887. Though the new model would likely have gone into production immediately after approval, it did not go into service with troops until 1888 ...)
Cam - can you supply any other photos - e.g. over all view, close-ups of the sights (front in particular) and the buttstock markings? This is intriguing - rather than having a MKIII upgraded to MKIV as you first surmised (not really possible, as I mentioned earlier, because of the significantly different MkIV receiver) it definitely appears that what you have is a very early production MkIV, made when MkIII parts were still being used up .....
I am still not able to give you a more accurate idea of value - since that is heavily dependant on over-all condition of the rifle, and even your locale - though the evidence that it is a very early production MkIV may very well add some value. With your permission, I am thinking we should post about your rifle (hopefully with more pictures) on the "dedicated" Martini-Henry forums at both "British Guns Forums" and "British Militaria Forums".
(I'm a "regular" on both sites, and even one of the moderators on one of them, so I can "take you along and introduce you", so to speak .....)