OMEGA deployant buckle will NOT work with standard tang-buckle strap.
Look at the photo below. White strap is standard tang buckle, brown is original Omega made for deployant clasp. One half of both straps, the one on the left is OK for any buckle, no problem. The problem is on the other half. The one for tang buckle has a cut in the middle + keepers that will not work with Omega deployant. Now look at the brown one -> it's clean, has straight uncut ending and no keepers.
On the right hand side you will see two watches where the top one is with Omega deployant - note, that one part goes underneath the other. What you need is an after market butterfly clasp, that someone was showing before, or foldover clasp that you see in the right bottom of the photo - this one is made to replace pin-buckles.