Hi guys,
Thanks for the interest and questions.
Regarding a date, I would place this in the very early 19th century for the mounts, but more likely in the 18th century. This is mainly based on the box like construction of the guard, the multi sided grip and the iron pommel.
The cleaning and rust removal was more or less just time (about a week) and the usual sandpaper/WD-40 combo (I usually use ballistol but was out). I also use a mildly abrasive polish to deal with the worst sections of rust.
The blade length is 75cm and the width at the base is 3.5cm. I'm attaching an image to show how it compares to some of its "big brothers" in the collection.