Yes, you have to remove the forearm to see the marking on the front of the frame. But, as Calhoun stated above, we don't know exactly when Savage started doing this, so your rifle may not be marked. My 1919 Model 250-3000, #208XXX is not marked.
OK, I removed the forearm and checked. This is (still) serial # 5037xx discussed above. There's an X on the flat just forward of where the rotor screws inside the receiver. The X is very exact but also very stark, two very thin and straight crossed lines... not like the relatively fat "font" characters from the (stamped?) barrel markings. (Maybe the X is etched, not stamped?)
I need to correct something I said earlier. The forearm itself has no markings, no serial number, etc. (My old notes are apparently not as clear as what I thought I remembered.)
