The ballista in the medieval world was essentially a giant crossbow and came in a variety of forms and mountings as far as the evidence suggests. It was an anti-personnel device, and could be used on the open battlefield or in attacking a castle, but seems to have been quite widely used as a static defence of gates and other areas of a fortification. The usual form of ammunition was the bolt, and the frame came in many designs, some offering more freedom of movement and control.
The model in this set is mounted on a rigid wooden frame, so seems intended for the battlefield. This frame has no apparent means of changing elevation, but could have been turned simply by picking it up and moving it. Its simplicity means it is historically realistic, although most examples probably had more to them than this one. It has a choice of bows, the only difference being the extent to which they are drawn, and a crude representation of the screw winch by which the bow was set. There is nothing loaded in the weapon, but one of the attendant figures carries a number of balls, which is quite possible but not the norm.
The kit itself presents quite a challenge as the pieces are not sharply defined and not as straight as they should be. Most are also attached to the sprue using vast amounts of plastic (see sprue image) so it is quite a task to remove the piece and then trim it. This is especially true of the bow, but everything is too flexible and roughly finished, and there is no attempt at precise fitting - everything simply buts up against its neighbour so requires a good glue. A skilled model-maker can produce a decent result, but it should not be so hard.
The four crew figures are pretty ugly examples of the type, as are many from Mars. Their costume, which is largely ordinary civilian dress, is fine in terms of accuracy but the sculpting is crude and the faces very bad. There is also a great deal of flash on them. The poses are acceptable, however, including one man apparently holding the winch handle.
This is a pretty simple kit which is not well produced either in terms of the machine parts or the humans that serve it. It will take some time to trim and straighten the parts, and to tidy the figures so they can be presented or painted, and the final result is not pleasing to the eye. Historically everything is reasonable but this is not a pleasure to make or to look at.