Isn't the more simple answer here that it is not an actual Rem Rand frame?
Exactly.
In 1967, I purchased what I
thought was a Remington-Rand 1911. It had the proper Remington-Rand markings on the slide, but the frame had
no markings except for a faint, but legible, serial number. At the time, not knowing much about GI .45's, I just accepted that it was a Remington-Rand gun.
Later, I researched the serial number and discovered that it was in the
Colt commercial range, but after the last known commercial Colt 1911 produced at the beginning of WW2, and before commercial production resumed after WW2. Wow! I thought I had a rarity!
Still later, in talking to some experts, it turned out that this was not a Colt frame at all. Most likely, this was an aftermarket frame, produced in the Philippines and imported in the late 1950's or early 60's. Some of these had cleverly devised serial numbers in the "nonexistent" Colt range, and some had no serial numbers or other markings at all! (Serial numbers were not required until the Gun Control Act of 1968.)
Someone had used this Philippine-made frame and assembled a gun using surplus GI parts, including a Remington-Rand slide.
Something like this may be the case with the OP's gun. The only thing that would argue against this theory is the faint "ordnance wheel" stamping on the frame. Could the Filipinos have faked that? I don't know.