Pete Klein :- What you see 99% of the time are fitting/crimping areas used to move metal inward to
fine tune the fit or to re-fit at a later date. Also at the top and bottom of the ana you often see areas which denote prior placement of kuchibeni/sekigane which is sometimes lost. Actual tagane mei are very distinct strike marks around the nakagoana. A classic example is from Kamiyoshi, Fukanobu used two at the top and five at the bottom, Rakuju two and three respectably. I am not aware of Hayashi or Jingo using them although the work of Hirata Hikoza often has rather large indentations along either side of the ana, usually five to the side.
Here you will see the two / three tagane mei of Rakuju:
Hikoza worked primarily in copper but also did some examples in iron. The copper had this type of lateral tagane however I do not believe it is considered a true 'tagane mei' although it is a kantei point of sorts.
Note the lateral sequential tagane of the TM tagane mei. Many of the works were signed but the tagane were a good way to differentiate them from later Akasaka and Higo pieces.
It is always good to remember that there are inconsistencies in all of these schools and also copies so these are only a part of the puzzle.
99.9% of the time the tagane you see are for fitting the piece. It is a mistake to read into these too much. They are used as a form of signature by specific tsubako only, just as kuchi beni are used by specific makers/schools. In other words don't knock yourself out looking for these and attempting to figure out what every little mark might mean. It's important to remember that these were made for utilitarian purposes.