WBD–I assume the numbers on centerfire do mean the same, but I can only vouch for the rimfires for sure. When George Kass and myself were writing the “Rimfire Headstamp Guide”, we observed the little numbers starting in 1981 and at first did not know exactly what they meant. But, as each year went by, 1982, 1983, etc. we noted that the boxes of HP rimfire coming into the US always had the number corresponding to the last number of the year they were imported and no other number. That is, in say 1984, you NEVER saw a 5 or 8 or9, etc. ONLY 4. It was clear by the time we included this headstamp in the “RHG”, that it was a year indicator and not a lot number. Also, note that the only numbers you see are 0 to 9. If they were lot numbers you would expect to see 14, 18, etc.