Ink bottle. I have the same ones only no embossing. I was told that mine were shafer skript. My dad said the pocket was to hold ink so that you could easily fill a fountain pen. Someone also told me mine was only worth $2 to $3 but was worth holding on to. Maybe the value will go up considerably in the next 20 or 30 years. Swiz
actually its pretty cool i got lucky and had the pat number on the bottom so i looked it up and saw the original documents written by the designer.....He explains all about why he made the pocket.....check it out - http://patimg2.uspto.gov/.piw?Docid=01759866&homeurl=http%3A%2F%2Fpatft.uspto.gov%2Fnetacgi%2Fnph-Parser%3FSect1%3DPTO1%2526Sect2%3DHITOFF%2526d%3DPALL%2526p%3D1%2526u%3D%2Fnetahtml%2Fsrchnum.htm%2526r%3D1%2526f%3DG%2526l%3D50%2526s1%3D1759866.WKU.%2526OS%3DPN%2F1759866%2526RS%3DPN%2F1759866&PageNum=&Rtype=&SectionNum=&idkey=4C50EABECA9F
Now you may not notice but its not text they are images copied into the computer from the original....It hard to spot it but it says 1 out of 4 pages....Make sure to check out all of them by clicking on Front Page, Drawings, Specifications, & Claims. This is an extremely informative site once you figure out how to use it. (www.uspto.gov) I love getting patented items so i can look them up.....It even shows when the patent was filed (so you know when they began making the item your looking up)