I was able to identify the manufacturer of our milk bottle. It was made by the Illinois Pacific Glass Co. and was either made in 1917 or 1927, as indicated by the single number 7 next to the logo. In the 1930s they used two-digit date stamps. So... I'd be willing to bet the bottle was made in 1927, shipped to a dairy sometime after that and made its way to our basement in the early '30s.John ("now that I'm an amateur archaeologist") mentioned that some years ago he found a 1950s-era vodka bottle in an area that was once a rubbish heap near the CSJs' convent. The area is now a shrine. That's another fun one to muse on -- how did it get there? (And who consumed the contents?)
The larger point, though, is something I tell my San Jose State library students: Given enough passage of time, virtually anything will become valuable. That makes preservation decision making interesting, because you can see the easy argument for trying to keep virtually everything. We all know people who do this. Lone Arrangers know better.