It will cover (sharply) a plate about equal to it's focal length, or a plate with a 70" diagonal. Artars are generally acknowledged to cover about 46 degrees, but they will at least illuminate quite a bit more than that, much of which may be perfectly usable for contact printing.

Focal lengths longer than about 35" tend to bring relatively less because as one person noted, very few people have both a camera that can support it and enough bellows to use it.

The "sweet spot" for Artars is IMO 30" and 35". possibly up to 47-1/2" although that's stretching a bit. In these focal lengths a larger number of people can use them and there are few alternatives. 24" and shorter, lots of choices and Artars bring much less.

Your lens is rare and has some value as a collectors item, especially with the box, caps, etc. Coated 30" and 35" Artars will bring $750-1000 in barrel on a person-to-person sale, and $1,300-$1,500 in shutter (based on eBay sales and personal purchases over the past two years). Red Dots will bring more than non-Red Dots, and pristine coated lenses with caps and box always bring a premium. Your lens seems to have a 78XXXXX serial, so it's a coated lens made just prior to the Red Dot series. I'd guess your lens would be worth $2,000 - $2,500, but that is a guess and you will be looking hard for a buyer unless it's bought for the collector's value.

Hope this helps.

Cheers, Steve