Ever is a strong word and without knowing the serial number of the gun in question, I cannot properly answer your question. The late Tom Dance in his book in the chapter on teh 106 sereis said "The reader should note that only the earlier models came equipped with the red bottom magazines, and all of these were inscribed on the bottom with HIGH STANDARD in white letters". One might infer from this that he believed that the change to the metal base occurred before the end of the 106 series which he placed in "the fall of 1968 at approximately serial number 2,030,000".
I would offer my observations.
Dance's 106 chapter has an unusually high number of errors.
The change to the 107 series began in late spring per the factory records ( the same factory records that Dance used per his second last paragraph of his introduction I would note that I find a lot of differences between what Dance found in the records and what I find in the records.)
The 1968 catalog was the last to tour the advantage of the red base magazine.
I have a couple of boxed 107 series guns with the red magazine and have seen a number of others. Note that these are early 107's.
Dance does not mention that there were two generations of the red base magazine.
THere were a couple of batches of 106 series guns - I beleive all Supermatic Citations and Supermatic Torunaments - produced well after the 107 series was introduced. One group has shipments in April 1969 and one group around August 1969 and the later group had shipments as late as February 1970.
In my opinion, the 106 series was gone before the introduction of the metal magazine base for the military grip models. The earliest of the 107 series pistols continued to use the red base magazines. The change to the metal base occurred after the 107 series was introduced but by the time of the 1969 catalog they had decided to replace the red base with the metal base or perhaps they had already done so and had exhausted the extant stock of red base magazines. However the two late production lots of 106's probably had the metal base magazines.
Not to my knowledge--I believe John and the Tom Dance book both state that the red plastic bottom magazine lasted through the 106 series and in to the 107 series.