That's the problem. I don't have any code or anything else that could be interpreted as the date of manufacture.
I guess they don't use one or have one on their batteries. Unless someone can tell me what number where, etc. RE13BV is stamped or etched near the top. Supposedly some sources say that's it. I don't think so. BV or BU, I don't know.
Sure doesn't seem like a date code to me.
dc