If you need a durable steel buckle for your belt project, get it here. And if your DIY airplane building project is at a stage where you are installing seats and seat belts, here is a proper steel buckle for those shoulder straps.
After climbing in your F-14 Tomcat cockpit and getting your harness on, you tighten your shoulder straps with these buckles. This steel buckle is strong enough to keep you in your seat during all extreme aerial maneuvers, Immelmanns and such. If you are not interested in aviation, you can also use this buckle for other purposes, like a unique belt design. The buckle has a slot for a 1.0” / 25 mm pull strap. The tightening mechanism takes a 1.75” / 45 mm strap. The buckle has a knurled bar, which slides and locks the strap in place when tightened. The buckle itself is 2.5” / 64 mm in width.
For your own belt project you'll need a length of suitable strap, one tri-glide buckle or zero tri-glide buckles and some sewing skill.
This buckle is unused US surplus.