HDA and K casting marks, TR7 head?

I have a new old stock head for a TR7. Sold as genuine Meriden, not Harris. I'm having doubts. I have two T140V heads and another TR7 head and these all have HDA cast onto the raised pad within the exhaust rockerbox cavity. The new one has the same part number as the other TR7 head but with the letter K instead of HDA beneath it. It also has the number 2 on the right hand side of the pad and the letter X at the bottom.

Anyone happen to know what the K lettering denotes? If it means it's a Harris head I need to know!