This is from a thread about Remington barrel markings on rimfirecentral.com. They are specifically discussing the heart shaped stamp. No idea if this helps..
“ 'Heart shape' in bbl. code
driver69911 - to add a bit more to what edlmann mentions above, the 'heart shaped' proof mark is the Final Inspector Proof during that timeframe. If yours looks like the pic below:”.
https://www.rimfirecentral.com/threa...stamps.494462/