Who is into old bottles??

I figured it was probably from the 20's or 30's, the seam runs top to bottom, and on the very bottom of it is a symbol that has an oval shape going up down and then side to side it has arrows. On the left side of the symbol, it looks like "18" on the right it looks like "b" in in the middle of the oval it looks like the number 1. I cant see how the top comes off, how can I clean it??
Thanks for the input!!
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