In the 80s I corresponded quite a bit with Malcolm Appleby, who engraves a lot of things, not just guns. At the time he was doing his series of magical "totem" guns for David McKay Brown, and had already done a sidelock feathered like a woodcock. He wrote in part:
"[It is] very important part of the function of a sporting gun apart from the obvious. To create a totem object that is personal to the user. This engraving may have no connection with shooting but in conjunction with the complimenting of form help to (hopefully) create a unique functional object that is powerful enough in design to be its master's mascot. There is nothing new in this it is as old as weaponry itself, but somewhere during the mass production the idea has been lost. Because of this line of thought it naturally extends to the gun itself. Had worked on sidelocks for years but was introduced to the ergonomic roundaction as now built by D. M. Brown. Not such a good weapon to show off engraving but a much more sophisticated design problem."
He added: "After woodcock gun sidelock did round action crocodile/snake gun (both beasts of great magical power.)"
I am putting images of both the raven and the crocodile below; I love the raven, but I think the tactile surface of the crocodile is even more amazing.