Cooke, Troughton & Simms Ltd of York theodolite?

I'd say that telescope was made towards the end of that manufacturer's life, probably 1840s-1868. The pivoting lens-shutter and the slip-on lens-cap (missing) were later innovations.

 

Thanks guys! How much do you think I could get for it?

 

Hmm. That depends. How long is it?

A pocket telescope (closed length approx 6-8in, open approx 18in) - they go anywhere from $100-$300 depending on condition.

A naval telescope (closed length approx 12in, open approx 3ft), go for 200-400 dollars, again dependent on condition.

This one doesn't have the lens-cap. That's going to affect the value since people who will pay a lot of money generally want the WHOLE THING. I'd say put $200 or something on it and see what happens.

If you pull it apart, clean it really good, blow out all the dust and wipe off all the grime, you might get more for it.