Thanks for the extra pictures, I find them very interesting!
The only two items that look familiar are the stirrup and the little plate that goes between the stirrup and the prod (the bow). That stirrup is the same one on the the MKIII and MKIV Cheetah and Quadro, and it is made from glass reinforced plastic (GRP).
The little pate was present in some versions of the recurve Cheetah Crisbow. The Cheetah and the Quadro shared a common GRP frame but the Quadro had a compound prod. There were some differences between the buttstock lengths also, amongst the various models.
Your MKI is most similar to the imbuia stocks of some of the Crisbow models. I have a Quadro with an imbuia stock but that one has a steel stirrup.
This is the Crisbow Quadro 2000 with the imbuia stock: (Edit: just noticed you also have one of those)
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The thing that fascinates me about your MK1 is the trigger mechanism and the latch and sight assembly. I assume the safety is the lever marked here:
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Am I right that it engages as soon as the string draws into the latch?
Do you happen to know if the bag came with the bow, or if it is a rifle slip that the previous owner happened to use for that bow?
Very interesting all the same!
That reminds me I need to update the Crisbow thread I started some time ago because all the Photobucket images are gone...