Recently acquired a Charles Ingram SLE with 26 in fluid steel barrels in excellent condition. The only serial number (AK56) is on tang of trigger guard. The barrels have all proof marks and markings but not a serial number and there is not any numbers on the forend. Is this a practice of Scottish makers? Any info would be greatly appreciated. Would like to determine age. The proof marks appear to be in 1924 to 1954 with Reproof marking LR 85.