No, the mark in the circle is correct for that era.
My Miroku / Browning side-by-side is marked BB2 in a circle just like that, for the year after, 1976.

The first letter is the year letter, and the second just signified Birmingham. The number relates to its owner working at the Proof House, so not the most senior chap, but his number two.

By the by, my Miroku is stamped "Made in Japan and assembled in Korea". I didn't realise they did that.

HB