I have tried several methods for de-rusting tools and have always had my best results from scrapping and abrasives. The chemical methods will do a better job with halting rust in deep pits but normal preventive post cleaning efforts will generally take care of that anyway. My restoration projects are normally limited to getting the tools into working condition instead of trying to get them “factory fresh”. The medallion isn’t familiar to me either and it might be that the “Sheffield Warranted” marking might be an equivalent to the American ” Warranted Superior” markings, meaning that it could be a general hardware outlet “brand” or “homeowner” level item (just guessing). Don’t feel bad about keeping it around for a while before starting on it. Someday I hope to get around to about a dozen of them that I have gathering dust right now.
Be sure and post the finished saw. We would love to see the finished product.