165OT correlation of knife serial number vs. sheath style

[Bridgeman]

If I have it correct, the sheaths used for the 165OT were:
1) riveted, angled retaining strap across the finger guard
2) riveted, transverse retaining strap across the handle
3) No rivets

Does anyone here have an approximation as to the serial numbers at each change? Or at least a range, or highest/lowest SN observed with each variation?

Thanks,
Greg