Since the “front buckle” sculpt is nearing completion I took a look at the functional “side buckle” and the leather belt itself. The best “images” I have to work with are from the toy collection which are “straight-on” to the buckle and a couple of screen captures taken from the front showing the buckle off on the right side. I am including an attached diagram to help with this discussion.
Consistent with all the images available I believe the side buckle is clearly a roller buckle which is taller than it is wide. Using the “toy” belt of 1.75”, the roller buckle is approximately 2.5” tall and1.625” wide. The buckle has a single prong or tongue attached to the end bar of the frame.
One end of the belt is attached to the end bar of the buckle. No details are available but I would suggest wrapping the belt around the end bar and sewing it as a permanent attachment. This would require a prong slot to be cut near the end of the belt. Again from the “toy”, the belt has two leather “keeper” loops. Each keeper is approximately .375” (3/8”) wide. The first keeper is set around the belt as close as possible to the buckle's end bar. The second keeper is approximately 2.5” to the left of the first. The total length of the belt should be long enough to circle the body, pass through the frame of the buckle and both keepers – and still extend approximately 2” beyond the second keeper. Note this is a belt which is much longer than a normal work or dress belt. For large waists like my own, there are no common leather belt blanks which will be long enough. (Normal cow hides are just not big enough to cut a blank in the usual way.) That will require either cutting the belt at a bias (angle across the hide), going with a larger animal, lapping two shorter pieces together, or going synthetic. Smaller waists should/may not have a problem.
The free end of the belt is square cut across the width of the belt. The belt end also tapers from the full 1.75” width down to 1” at the end. This taper is regular and symmetric so the 1” end is centered with respect to the full belt width. The tapering “appears” to start 2” from the end, just as the belt exits the second keeper. Note if the taper begins too soon, the belt end could flop up and down in the second keeper. As such, you may want to make the belt extend slightly more than 2” beyond the second keeper, or make the taper run less than 2” to ensure the taper does not start too soon. In any case you want to delay making the final length and taper cuts until you are sure of the overall fit of the belt with all the accessories and pants you will be using with the belt. Start construction at the buckle end.
Holes are punched into the free end of the belt. Holes are in the center of the belt's width and placed approximately 1.5” apart. Holes seem to start with the exact hole the prong is inserted into for the proper fit. Again this means you probably want a few test fittings before final cutting and punching. Note this could mean the holes start five inches or so from the end. This is a very unusual situation and with additional images we may find the holes do start closer to the end. However I like the clean look of the unpunched belt end. The count of punched holes should be enough to come around the body from the right to the wearer's center-front. This is the position of the “front buckle”. From the images there is one hole to the immediate right and also to the immediate left – giving a measure of 3” across the central section of the sculpt. Both of these holes are located inside the buckle frame which the belt passes through (behind the sculpt). There are at least two more holes to the left of front sculpt buckle. Holes “could” repeat along the full length of the belt as a “design” or “decorative” element but there is no evidence of that as of yet. Again the “toy” does show holes going off to the left– but it does not show them coming around from behind the back and continuing to the wearer's right side and beyond to the end bar attachment.
Fortunately there is some flexibility in the hole placement during fitting. I believe there “must” be a hole at center-front. This is where the back stud of the front buckle will be inserted to hold the buckle's position centered to the wearer. Holes then go in both directions with the 1.5” spacing. The wearer's waist measurement will determine how far right-of-center the side buckle will be positioned. It definitely needs to lie before going all the way to the wearer's right side. With this in mind, I would start my fitting by deciding approximately where I want the roller buckle to be located. Where it will not “dig” into my side when I bend over or twist. With this decided, mark the center-front and use that to set the center-front hole. All of the other hole locations and belt “landmarks” are relative to this hole. Once completed the entire belt can be shifted left or right as necessary (around the waist) to keep the front buckle centered. There are no pants loops which would restrict this type of movement.