It has occurred to me that in trying to identify the M mark on the 1 Pr projectile that If no 1 Pr. Maxims were made prior to 1889 then it can't be a Maxim Gun Co mark. If these guns were only produced from say 1890 on then while the M mark certainly stands for Maxim, The firm was the Maxim/Nordenfelt Co and this mark proceeded the better known MN monogram.