Sega Saturn long life battery

Very cool. I bought a CR123A which I'll be adding this week to my Saturn. I couldn't find the SAFT LSH 20 here in Japan.

 

Anyone knows what battery it is - 3.3v 20Ah, rectangle and flat, about a half of a compact cassette case in size, looks like typical 60s high voltage 10-50uF paper capacitor, only in a plastic case? Got it from dead repeater station about 10 years ago, it wasn't new but it was enough to power a HUGE quartz clock for 9+ years and there's still 3.25v left. Label was damaged so there was no info except voltage and capacity.
It will be great if it's a some standard battery because it will fit easier than LSH 20 in Saturn case and will run longer, waaay longer. If it's some proprietary battery then it's bad because there's a huge chance that those aren't produced anymore or extremely expensive.