Hi PBK. That is a nice link you put up. The images on it looked familiar though, and after checking, I see that images X, XI, XII, and XIII are the same drawings that Ross Whitehead produced for his volume on "Buckles 1250-1800".
Just so FooserPaul understands: although the images in this scan are labled "c1660-1720" in the top heading, they are actually 1660 to 1790's. These original drawings produced by Whitehead which are used again in PBK's chart, give specific dates in the original text to all of these individual examples (which again, are used on this chart and are re-labled X-XIII.) (In fact all of the drawings on this chart are individually explained by Whitehead throughout his book) .
For example image X (which Whitehead labels "VII" in his original study) is dated by Whitehead to be between 1720-1770, as are the next two (your image XI and XII). The next image in your chart labeled "XIII" is the loop chape Whitehead mentions as consisting of a steel double pitchfork, and that one dates after 1770 (1770-1790).
FooserPaul, it is confusing (to me too) why the chart here is headed "figure 9 1660's -1720's, yet when you look underneath you understand that the drawings conform to Whitehead's dates of 1660 to 1790's. In other words, when you go to the original source and see dates clarified you find that your loop chape dates between the period of 1720 and 1770, but not earlier.
