As my buddy Joe say's...stop the presses! That's a baby dot snap on a Heiser. Good eye Tom.
Ronnie, it is not a baby dot. I don't think the baby dot was even around when that sheath was made. I am not sure why there continues to be some doubt. Heiser used various metal snaps throughout their run, but not a baby dot.
That particular snap is larger than a baby dot and is constructed and fastens differently. It also looks different. Notice it appears to have been painted too.
As a footnote, I think the baby dot type is patented. It has a metal "wire" set inside the female portion that has a gap (not continuous) which allows it to expand and accept the male portion then contracts back down on the male. Thus the better holding power and durability.
Here is a similar sheath:
http://www.rmkcollector.com/index.php/for-sale/accessories/rare-wwii-vintage-heiser-sheath/