The Ishapore plant in India was operating around the early 1920's and was run by the British (Colonial thing). After 1947 or so, the plant was taken over by the Indian Government, and #1Mk3 rifles in .303 were still being produced. The newest .303 Ishapore I have seen was from the 60's, but I am not an authority on them (mine is a 1950). Around the early 60's, Ishapore "modified" the design, converting the Mk3 to .308, and redesignated them as 2A1's.
Identifying an Enfield is easy. Look on the butt stock socket on the right side, and list the numbers and letters. It can then be positivly ID'ed with the manufacturer plant (BSA, LSA, etc.) Your 1918 (probably a BSA, as they were the most common) is probably typical, and $240 is a good deal these days.