Can Anyone identify this vintage Rolex please?

[Gadget Man]

Hi Guys,

I was having a conversation with a work colleague the other day and we got onto watches and Rolex's, he tell me that he has his fathers old 1950's Rolex Imperial, which I had never heard of.
Anyway, he brought it into work and I took some photo's of it. He says he remembers that his father had the bracelet replaced in the 1970's and thinks the crown was also replaced on a service too, the rest of the watch is original. It is in good working order but he knows very little about it.

Can anyone tell me (and my friend) anyrhing about this watch and is it collectable/valuable?

The words on the dial are:
'Rolex Oyster'
'Imperial'

'Extra Precision' (around the seconds dial)
'Swiss Made'

The crown has the words 'Oyster Patent' written on it, no crown
The case is stamped with the numbers 127431 and 2595

Many Thanks

By the way, sorry if this is placed in the wrong place, moderators feel free to move it.