The 721 is pretty close to a 700, the biggest difference I'm aware of is the extractor ring in the bolt face. Rather than having an extractor milled into the bolt face, the 721 has a ring of rolled/stamped metal that clips into the inside of the bolt face.
This ring is relatively weak compared to a 700 and occasionally breaks.
I thought all the original 721's came in blued steel.
the one i have was made in 1956 and it does have a stainless steel barrel i had a friend that is really into guns check it out he said it is stainless he said it is probably a rare one the letters on the barrel say it was made in 1956
When it comes to scent, there are basically two types; those that attract and those that mask. I've tried both on many occasions. There are lots and lots of "doe in heat" scents, designed to attract a big buck into range. I've also used a "cow in heat" scent while elk hunting.
Another scent would almost be better named as a "coverup smell". The main goal is to cover up human odor or mask it. Though I don't believe you can ever totally eliminate all human...