Better pictures (in focus) and more of them, would help to verify what you have there. As was stated, the original SAA's were delivered to the government with 7 1/2" barrels and one piece walnut grips so it has definitely been altered if it is one of those delivered to the army.
Is there a U.S. stamped on the left side of the frame below the cylinder?
All of the original Colt SAA's that I have seen that were sent back to the factory in the 1890's to be refurbished and have the barrels shortened to 5 1/2" have mismatched serial numbers. Your pictures are too out of focus for me to really see the if the triggerguard and frame numbers still match, but if they do and it IS a ordnance ordered factory rework, it would be unusual.