The French Darne* Sliding Breech Shotgun in 12 Gauge

Happy April Fools Day! Hope y'all are staying safe out there! Shooting my new (old) Darne clone in 12 gauge. This shotgun sports a unique action in which the breech block slides back to allow the user to chamber as well as automatically extract spent shells. This shotgun was originally chambered in 65mm (2.5") shells but the chambers have been extended to accept 70mm (2.75") shells which you can see on the barrel flat in the gallery of this video. *This particular shotgun does not sport the Darne logo and instead is inscribed: "CANON ZF FIXE". It is my understanding ZF stands for Zavattero Frerres, an experienced canonier established from 1880 until 1965. I do know that the Darne patent expired at the turn of the century and a number of high quality clones entered the market with the design. Mine seems to be and it appears it was even used in a Grand Prix in Milan (1898) and London (1903)!