I've never seen a 'toothless' Model 18.

I've been reading the RKS Newsletters, however, and there is a photo of a Model 18 crutchtip on page 6 of issue #26 (March, 1995) which looks to either have no teeth or teeth so small that I cannot make them out. The accompanying article discusses combat used RMKS, including Col. Joe Kittinger's Model 18, but does not specifically reference the pictured Model 18 (nor does the photo caption mention that the knife lacks teeth).