Yes me too. My LSA SMLE is ‘O’ prefix (I had to spell out to my local firearms licensing dept that it was ‘oh’ not ‘zero’). In regards various SMLE production across the types and years, LSA used an ‘O’ and I believe Enfield used ‘I’ and ‘O’ serial prefixes.
I believe Maltby were particularly untidy in how serials were applied by hand. The person who stamped my No4 must have had bad eyesight and been standing on a slope!