Approximate value

My guess is a 550 based, or 601 based watch (Depending on automatic vs hand-wind), so 60s or 70s as you say. They are a bit a dime-a-dozen/are pretty easily obtainable. Model number would be inside the back case (and that would let you see the movement).

I typically pick them up in the $300-$400 range if they have a nice dial, hands, and case, and in need of service. The one you have is obviously a very bad case (so not really 'good condition at all) thanks to the damage from that bracelet, but the dial + hands are nice. IF I saw it on ebay, I MIGHT put in a $300 bid, but I'd probably skip it unless I had a nice case to pair with it already.

So unfortunately, as Davidt said: ~250 GBP at the high end, I'd say ~$300 USD at the most, so we're not far off.

IF you're interested in selling, I'd suggest taking a bunch of really good photographs and putting it on Ebay to see what you could get for it.

Look at the top lugs, both are basically 1/3 of the way cut into. Bottom left is also bad, but the top ones are both worse than that.