It is actually the fourth variant, as it has an oval trigger guard aperture, whereas variant three has a quadrant-shaped aperture. It can also be distinguished from variant five by the rounded, rather than squared-off, base to the grip.
These are fairly late items, for a Dolla, and were advertised beteen 1927 and 1940, and although once to be found regularly at arms fairs are now quite rare. In this condition, and assuming it has the correct breech pin, I would value it at about £60-70.