Thank you! I suppose the crop of breweries then will one day be replaced by the micobrews of today for collectors of tomorrow. I still live in Pittsfield, if I learn anything from a local I will drop a note back here.Unfortunately, finding information on late 1800's-early 1900's Massachusetts breweries is generally very difficult as they are not well documented online or in general- there are so, so many beer bottles from Massachusetts (especially in Boston and cities near Boston) in addition, which blurs things even more. I did find a couple small things: judging from this Pittsfield MA community development document here, he was located at 49-55 John St. If it is in fact the same John Downs. He occupied the residence in 1881-82 and looks to have owned it into the early 1900's, which would match the timeframe for your beer bottle to have been manufactured. It is unclear if this was home residence, business residence, or both. Here's the document: https://www.cityofpittsfield.org/city_hall/community_development/community_development_and_housing/docs/Project Description 49-55 John Street.pdf
and the important passage: View attachment 217649
In addition, it seems there's another beer bottle embossed "Downs and Welch" listed on Sodasandbeers.com, also from Pittsfield, which would mean he had a business partner at one point. There is also a rare Hutchinson soda bottle with his name on, so it appears he also sold soda. It's not much but hope this gives a tiny bit more info on it for you!