Thats a fantastic find ! Thanks for posting up.

So the photo shows Feb of 1970
Any idea what the 209 represents?
Where the date wheel and 209 embossed on one of the sides or bottom?
Was there any indication of anything stamped into the top of the positive or negative posts?

As added information, the ICCA manual provided an example of a cross with K, C, 1, 2, where each symbol is stamped in a quadrant on the positive post. On the negative post was an offset vertical line and the numbers 673. No example was shown of a date wheel or other embossed/impression marking, but the photo is labeled as a 1973 group 27 battery. With none of this explained, how would the author know this was a 1973 battery? Perhaps a leap of faith that the "673" on the negative post was June of 1973, leaving one to wonder what everything on the positive post represented.