A friend of the family has got a Milbro G4 air pistol. Does anyone know if this is worth anything or is collectable?

It is in its original box, rust-free, 6 darts (don't know if they were supplied with the gun or not) and a tool for removing the darts (again, I don't know if they were supplied with the gun or not).

It says somewhere, on the box or a sheet, "New improved micrometer click action sight".

Judging by the style of box and pistol it could be 1960s.

Thanks.