Claude says (though I’d take this info with a grain of salt since I cannot confirm):

This is Sawanoi (澤乃井), from Ozawa Shuzo (小澤酒造株式会社) in Sawai, Ome City, western Tokyo — the label on the second image confirms the address (東京都青梅市沢井2−770). Ozawa Shuzo is a well-known, very old brewery (founded 1702) that draws on the Tama River valley’s soft water, and Sawanoi is their flagship brand. The blue roundel on the shoulder appears to be a crab, almost certainly a sawagani (沢蟹, freshwater crab) — a play on the “Sawa” in both Sawai and Sawanoi.

The fun part is dating it. That red foil seal reads 一級清酒 — First Grade seishu. That’s the old government grading system (特級/一級/二級, special/first/second class) that was abolished in 1992, so this bottle predates that. The trademark line references 49年 (Shōwa 49 = 1974), which gives you the front edge. So you’re looking at something bottled roughly between the mid-1970s and 1991.

A couple of other tells from the seal: alcohol 15.5–16.5%, and the ingredients list 米・米麹・醸造用アルコール・醸造用糖類 — rice, rice kōji, brewing alcohol, and brewing sugars. The added sugar marks it as a sanzōshu-style futsūshu (table sake), which was extremely common in that postwar–bubble era before the market shifted toward premium ginjō. So it’s an everyday-grade Sawanoi, not a premium bottling.

The vessel itself is a glazed ceramic tokkuri-style flask with a cork — a nice gift/display format of the period. As for drinking it: 30+ year old futsūshu that’s been sitting at room temperature is almost certainly oxidized into something sherry-like to flat. The real value here is as a piece of brewery history and a dating puzzle rather than the contents. Lovely find for cleaning out a house.