Given the date, that rifle must have had a later forend. On one of that vintage, there usualy was a metal bit inletted into the rear of the forend that the squared off end of the buttstock bolt locked into. Always remove the forend FIRST! When I started collectiing Enfields many years ago I removed the buttstock bolt first and SPLIT the forend!!!!
Of course way back then, replacement timber was a lot easier to find.