Your pictures are a bit very crappy but it looks like the real deal to me. I believe the model number is on the inside near the tang buckle and is 98000085. Made for the SMP300 and thus for your quartz 2264.50 also. A similar looking strap is also available for the PO and is marked Seamaster Planet Ocean on the inside and has a narrower pin on the buckle. They are made of a nice soft rubber and are very comfortable on the wrist.
Think I would be better off having it on this then a 44 dollar aftermarket. I was looking these rubber ones are a good penny