Quote Originally Posted by Tobor View Post
BrianQ,
Could you refer me to the M1icon Carbine reference where this is explained?

While there were only two entities manufacturing TSMG's during WWII, Savage and Auto Ordnance, and 10? entities manufacturing Carbines, it is odd that there wasn't a standardized finish that would be utilized for all factories for USGI small arms. Many USGI TSMG owners still believe their Parkerized Thompsons' sport the factory finish.

Phosphating is the same as Parkerizing (which was a proprietary process of the Parker Rust Proof Company just as " Du-Lite" is the name of a refinishing product) and would require that the parts be sandblasted first or the finish won't adhere. This would be a time consuming process and the parts would require protection from rust while awaiting the phosphating. There is no prep required for bluing other than the parts being clean. To machine a part, and then blue it is much faster than Parkerizing. The time savings in the middle of a war would surely tend to favor bluing, especially when the factories are already set up for bluing. The TSMG was subjected to the same government mandated proof testing, and yet they were shipped out blued.
Why are you digging in your heels on this, questioning decisions and processes of nearly 70 years ago? It is what it is. One of the early carbine manuals had the phrase 'a peculiar shade of neutral gray' describing the obviously Parkerized finish. Yes, we know that Parkerizing is Zinc Phosphate.