FS: Your very own Frankenbattery
These were a popular alternative for Yashica Electro 35 (GSN and the like) cameras using the old 5.6v mercury cell. What we have here is essentially 4 of the 640A batteries joined together by a small metal tab minutely spot-welded in place. Then production of the 640A batteries was ceased, so production and sale of these stopped. Well, I just found one in a box and it still seems to be fine. Still measures 5.94 v output. So, here are two options: if you have an Electro 35 or similar, use it as it is. You can remove the tape if you wish. Or if you have a camera which originally was designed for the 640 batteries, separate all 4 battery cells, file carefully the spot weld dots off and use them as 640 cells.
So, for $3 plus the cost of postage, you can have a battery for your Electro 35, batteries for cameras like the Olympus 35EC (as I recall) or others.