USOM is a one metre class mostly built and sailed in the USA, and they are lighter weight boats than the IOMs.
I think that they usually weigh about 5 1/2 lbs, and the IOM is 4Kg.(8.8lbs)
The narrower width of boat 2 is what makes me think that this is what you have here( less buoyancy )
I too would keep and sail the IOM, and you don't have to spend a fortune to get it on the water.
Fishing shops are good for braided dacron, dyneema or spectra line,also swivels, snap-hooks etc. ( also stainless wire for rigging)
Also look here for parts
http://www.pjsails.co.uk/Have a look here for a guide about IOMs, section 2.9
http://www.ivorbittle.co.uk/Talk to people at your local sailing water, and show them what you have; you might even get a scruffy old boat and be able to transfer all the bits!