Definitely a sidewinder. I own one and it is quite fun, although fairly old at this point. They were raced in the US in the '70's and had an optional spinnaker and trapeze which made them quite quick. They often go for around $800 on craigslist, although that one looks to be in pretty rough shape.
It is absolutely a Sidewinder. Yours was probably built around 1974. The divider on the cockpit floor was not cut away for cross drainage until about 1974 and Orange deck Sidewinders were not built after 1975 or 1976.
The above is a photo of a start in a "downriver " reggatta held on the Susquehanna at harrisburg in about 1975. 1999 is my fatherand Mother and my newlywed wife and I are on 2000. There was more current than wind so we could only race one direction.
Notice in the second photo in the first post at the top of the thread how the rudder and rudder head have a notched system for engaging the rudder in the down position. The rudder on Sidewinders would swing up and out of the water if the tiller was lifted and pulled foreward.
The committee set up a restraining rope hooked under all our rudders. At the start we all flipped the rudders up and drifted off.
Notice the body language difference in how old men wait for the rope to be released and how the young kid waited.
This was going to be a 22 boat line of boats. We still had to wait for the rest to line up and I was already straining and ready to cast off.
The boat is at least a 1975 as Older Sidewinders with that deck design had a 1.5 inch rather than 3/4 inch aluminum rubrail.
You can find more information here. Some of the old newsletters have names of owners. maybe you can find the person who originally owned the boat and trace down the spars and sails.
Pretty sure it's a sidewinder.
Are you interested in selling one of the centerboards? My son bought an old sidewinder after earning his sailing merit badge at Boy Scout camp. The boat was missing the centerboard and needs some minor (?) repairs. This will be his second summer with the boat but he has never been able to sail it b/c we can't find a center board. Your pictures are the closest we have ever come!
Let us know if you might be interested. I could send you dimensions of the original one that we found online.