Rob,
First English power flasks in America probably late first quarter to early second quarter of 19th C. So you can date the use of a charger from that era up to today I would think. Looks like a one off, from any era.
I may be off on the introduction of the flask to America but I think that is what I have read (not always right) or heard ( Once again, not always right).
I think the French were the first to use them but I would like to know more or be corrected.
Tim C.