I finally got home form the cottage and dug out my copy of Stratton "British Enfield Rifles Volume 4" and reconfirmed / remembered a few things
pg 26 Miscellaneous P-14 Marks
The "Emergency Use" mark, a 0.33-inch high Maltese cross, ins found on the buttstocks of a small number of very early rifles that the War Office found "doubtful." It indicates that the rifle should be used as emergency or for practice use only.
No clubing the Kaisers soldiers I guess. Anyway, give the crack in the stock and repair this marking is consistent with the condition of the rifle and indicates the crack happened before proof inspection.
I also remembered that this rifle is the earliest configuration, Mark I, not the more common Mark I*. The serial number range is 187###. I don't have access to information as to the approximate manufacture month. Given than Eddystone made 604,000 in 1916-17 this rifle is in the early third of production. The 1917 bayonet is not consistent but not really wrong either I don't think. Eddystone didn't make bayonets since the Remington factory produced enough for both divisions of that company.
According to Stratton there was a change in the design of the rifle that was implemented in December 0f 1916. This involved making the locking lugs longer as well as the recesses in the barrel. The revised rifles were designated Mark I*. According to Stratton Mark I rifles command a premium over Mark I*. Which is great as long as somebody cares enough to pay a premium.
Short of disassembling the rifle it would seem all serial numbers match except for the rear sight leaf. That is to be expected as I recently replaced the leaf because the battle sight was damaged (Opps - point of knowledge, do not fold back the rear sight leaf beyond vertical in try to close your bolt, you will catch the battle sight and stuff will break). The battle sight I had at first didn't match either and numerically the new one is much closer. I'm trying to make myself feel better here. Mis-matched is mis-matched.