FN is referring to the Randall Firearms Co, about 10,000 guns in several variations 1984-1985. There is some collector interest, boosted by a long section in Blue Book by somebody with connections to get a lot of space there. $700 would be a good price for one in excellent condition.
Now if they have a gun from a gunsmith named Randall dba Randall Customs, that is entirely different. I have not heard of a Randall Customs shop so you are on your own to judge the quality, condition, and desirability.
I have a few facts and a lot of opinions.