Barron was formed in 1980, so its 41 at the oldest. From what little detailmis visoble my gut call is early 80's.
Im no authority on trikes, and the market demand is somewhat limited. By somewhat I actually mean extremely. Nevertheless, its a reasonable quality frame and looks in generally good order. Put some tyres on it and a nice seat and it might be worth in the £250 range, but that's totally dependent on finding a buyer in what is a very niche market segment.
Conversely, if the seat post is seized in the frame itll be worth more broken for parts.