While waiting for the new blades to arrive for my 4.5 and my 8C - I went on a couple of the plane guru sites and discovered that my 4.5 looks like it is from the WWII era.
They mention that many of the planes from that period do not have the frog adjuster -- often never even drilled.
Why do you thing this was ? Was it just cost?
They did not save all that much by not drilling one hole!
Mine has no holes at all