This machine is an oxybeleis, something like a large crossbow, which was the earliest form of artillery used by the Greeks. Such machines first appeared around the start of the fourth century BCE, and were used to shoot both bolts and stones. This particular model resembles one designed in the middle of the fourth century, but was fairly typical as far as can be ascertained.
The stock of the weapon is roughly the height of a man's head, and the bow is a little over 2 metres long. The handles at the rear winched the bowstring back, a bolt was placed in the slider and the string was released.
This is nothing like as sophisticated as the Zvezda catapult. Each machine comes in three pieces, with the crucifix-shaped foot being one, the supporting legs the second and the catapult itself being the third. With a little trimming the pieces fitted together OK, and of course such a simple construction means it is built in no time at all. There are no bolts included, nor bowstrings. The winding handles are conveniently level with the stock, and like the rest of the model they do not move. The original was elevated by adjusting the support, but this model does not have that flexibility.
There was a good deal of trimming required to the pieces, but once that was done a decent little model was made. For such a simple kit it is surprisingly accurate given the limited evidence that has come down to us, and the most obvious flaw is that it does not come with any crew figures. Still it is by no means bad and if given a crew would make an interesting addition to Hellenistic armies of the time.