There are several klaplock crossbows in Churburg which are surprisingly early. Numbers Ch295, Ch318, Ch320, and Ch321 all appear to be from around 1500. Stylistically, there is no reason these weapons could not be a decade or two earlier. There tillers are straight, and do not have the asymmetrical cheek of the later bows.
In addition, there are numbers Ch 298 and Ch 299. These are thought to be from around 1500 as well, but I would date them to the mid 1500's.
Numbers Ch319 and Ch320 are described as c1500, but they look to me more like the first quarter on the 16th C.
There is also a group of light target bows of crude worksmanship which are thought to be from 1540 to 1600. They are numbered Ch324 through Ch 327. These wimpy little bows would make excellent SCA target weapons!
All of these bows are were described in detail by Trapp in the first Churburg catalog, but not illustrated. The Graff described them as having "iron nuts". The only tip-off that these were not roller nuts is that some were described as having an "iron nut" which was "missing". The publication of the new catalog by Scallini illustrates all the crossbows, and thus makes it clear what the Graff was trying to convey.