Mark wrote, in part:
"So the moulding is there just to register into the cut made by the snipes bill?"
In effect, yes, the profile of the side snipe allows it to register down into the quirk created by the snipes bill. Given the orientation of the iron and its cutting edge, the vertical cheek of the plane becomes, in effect, the sole of the plane and any cutting takes place laterally to clean up the shoulder, or sinking, of the quirk (and/or to widen it).
Some people have described the cutting action of a side snipe as a scraping cut. However, I think this actually depends on the skew of the iron and one's definition of a scraping cut. If the iron is skewed 30º from square, that results in an angle of attack of 60º relative to the cheek/sole of the plane, which is equivalent to half or cabinet pitch. So, if you consider half pitch to be a scraping cut, then that also applies to a side snipe. If not ... .
Peter Nicholson, in his Mechanic's Companion, uses the terms "sinking snipes bills" and "side snipes bills" which, I believe, helps distinguish the differing functions of the two types of snipes bill planes. With the increased interest in snipes bill planes over the past ten years or so, it is helpful to be aware that there are two types of planes in this category and understand their differing functions. So I'm glad you asked about your side snipes. It's been a bit distressing to learn of a handful of occasions where tool dealers have sold customers side snipe planes when they were in the market for snipes bill planes. Needless to say, this has led to a great deal of frustration when/if the customer tries to use them.
Incidentally, in our "study collection" we have a single snipes bill plane which has a wooden depth stop. Initially, I'd been inclined to think this might be unique to this plane, but we have since found a couple of mentions of snipes bill planes "with slide" (sliding depth stops), in older plane makers price lists. So, while quite uncommon, the use of a depth stop with (sinking) snipes bill planes, apparently, isn't unique to our plane. I'm attaching a photo of it in case anyone is interested.
Don McConnell
Eureka Springs, AR