I took some pictures of a 16th century Spanish Crossbow that was in a local museum. Thought I would share some pictures. Has some interesting features.
It doesn't show up well, but if you look in the bolt groove the light spot is a raised section. It looks like the bolt would rest on the roller but and the bolt rest and not in the groove. There is a small bone section in front of the roller nut and it is raised compared to the bolt groove.