I thought Ishapore guns were made in India? And weren't the later ones in .308? I always thought of getting one of those a few years back when they were so common, and now they seem to have dropped off the market.
Sorry, misread your initial post. I thought you were talking about a No1 rifle. Your rifle would be a No4mk2 if it's Pakistani, produced either as a Brit rebuild on Pakistani equipment, or possibly a new build.
Anyway, hazard a guess that it would be in the $175-$250 range, depending on condition and buyer. Maybe higher on AA or gunbroker. Hard to say without seeing it.