South Jersey Refugee Here.
I'm looking thru my reference literature and all the HRA serial numbers are 5.8 million and below.
Springfield receivers go to serial number 6099505. HRA stops at 5788594 according to Scott Duff's, The M-1 Garand: Post World War II table 6.4 on pages 84, 85.
Can you at the very least field strip this rifle and look at the drawing numbers?
$1250 would be a fair value for what was the Correct Grade HRA if the CMP still had them. I paid $950 plus shipping for a Correct Grade Springfield better than five years ago.