Gold Automatic Dress Watch - Runs Fine But Can Not Wind Up

I recently inherited this  watch from my father. I think he probably purchased it in the 1960s (possibly in Celon/ Sri Lanka in 1962).

If I "charge" it, by wearing it for several hours, and then place it static on a table, it runs for about 50 hours. But I am unable to wind it up manually as the crown will not turn clockwise.

I would greatly appreciate and information on the watch, inputs on why I am unable to manually wind it up, advice on how this might be resolved and whether this is likely to be an expensive repair please.

Many thanks!

Just to clarify. 

If I pull the crown out, I can move the watch hands to set the time. But, with the crown pushed in, I can not turn it clockwise, so am unable to manually wind it.