Hello Michael, and welcome to the forum!
That's an infill panel plane, and it looks to me to be user-made. Infill planes were expensive relative to a craftsman's wages, and panel planes cost more than the slightly more often found smoothing planes. They were intended for fine finishing work on harder woods by such trades as cabinetmakers, shopfitters and instrument makers (for which reason they often had very tight mouths), and as they were highly prized, it isn't unusual to find that some impecunious tradesmen made their own. User-made sometimes implies a bit shoddy, but as your example demonstrates, craftsmen often put a lot of care into making tools like these. I suspect that this plane was made by J.Welsh for his own use.
Quite a few tool dealers sold the parts to enable craftsmen to make their own planes, including cutting irons, cap-irons and screw caps. In this instance, the mark "Buck and Co" was one of several used by Buck and Hickman (according to Simon Barley's splendid book 'British Saws and Saw Makers'). Buck and Hickman was a very long-lived firm, so ascribing an exact date to it would be nigh-on impossible. Screw caps appeared in tool catalogues from sometime the 19th century until about WW2, which doesn't, of course, help us to date your plane either!
Sorry that doesn't really tell you anything definite, but I'm afraid I'm no expert on infill planes; hopefully someone with better knowledge will be along shortly.