Hi 'Nando,
the first crossbow has the earlier 'peg' release mechanism....as the draw weights increased (the energy required to pull the string back to the 'locked position) , as crossbow prods (bow) evolved....the 'peg' became obsolete. This was because the pressure of the string prevented the 'peg' from being 'pulled' down (via the trigger) to 'release' the string.
The 'dot' could indeed be where a screw/nail/ rivet held the 'catch'.... perhaps the rust marks where it once was....or the corroded remains.
The second crossbow has a 'fold up' aiming sight ....its difficult to see but it may have 'incorporated' into the design a 'catch'.
The bronze sculpture is most interesting, as you might know, I have always liked Benin bronze art......my avatar is the clue
. The 'cocking' device you termed the 'armatoste' is known as the 'belt and claw' in Britain ....your term sounds better
I did know that the Portugese introduced the crossbow to the people of Benin ....whose ruler saw the millitary advantage immediately. Unfortunately I have not been able to find images of the African useage or examples. I found this interesting though..........
".........The Portuguese arrived late in Ewuare’s reign, and he is the first oba to be linked with wealth and power derived from coastal trade. In Edo oral history, Ewuare is credited with obtaining the royal garments of coral (ivie ebo) and red flannel cloth (ododo) that were among the new luxury goods imported to Benin. According to legend, Ewuare traveled to the palace of Olokun, the god of the waters and prosperity, and stole the deity’s spiritually charged coral garments.
The Portuguese also added crossbows and firearms to Benin’s arsenal; however, the use of these weapons was limited to the oba and his commanders. In Benin’s visual arts, the Portuguese are strongly associated with Olokun and frequently appear alongside mudfish, crocodiles, snakes, and other beings that traverse between water and land, a trait shared by Portuguese seafaring merchants............."
All the best
David