Why Were Carbines Factory Parkerized When ALL USGI Thompsons' Were Factory Blued?

[Tobor]

Nope

What some fail to realize is that not all the manufacturers staked flip sights when they were initially installed. Methods varied among the manufacturers that did stake the sights. When rebuild facilities upgraded the rear sight they may or may not have staked the new sight in place. The same goes for sights that were installed at a lower level. To further complicate things not all adjustable sights were staked with a round punch, some were staked with a chisel type staking device. In order to tell the difference you need to know what each type of staking looks like for the various types of sights.

Would it be fair to extrapolate from this that the absence of these marks, or the presence of these marks, is not a reliable method to determine whether a flip sight was ever replaced with a ramp sight? Is there information printed since Ruth's books about which manufacturers did or did not stake the flip sight and by which method?