.22 rimfire headstamp

.22 RF long rifle rd:

Is this headstamp unusual ? the center part of the head with KN stamped is concave. I assume the KN means Kings Norton.

I haven’t seen a concave head before.

The concave head helps to ignite powder for RF ctges.
It is an old trick which is coming back nowadays on new 22 LR ctges
jp

Armourer, Kings Norton used that headstamp pre WW-2. I have several sizes and depths of the depression and shapes of the KN in the collection.

Gourd

Thanks folks.