I received this reply from Steven Summerfield, on the "Napoleon Series" forum:
Thank for the pictures. It is of 1-pdr calibre with the correct dimentsions of a M1757 Rostaign Gun that had been used up to 1795 on a small carriage. It is nice to see an another example of one. I need to find my book to give you details. An example in St Petersberg is 56mm calibre, 91cm long and weighs 77.6kg. It was adopted by the Gribeauval system. The carriage was simmlar to those you describe.
John Morris comment: I have asked him, on the other forum, to clarify some things about his post, such as the presence or absence of a monkey-tail, etc. While the bore and length of the St. Petersburg specimen match mine, closely enough, there's a large weight discrepancy I'd like to resolve.
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