Had a recent request for this one and thought it'd be a nice break from overdrives. Part of the Ibanez 10-series, it's a noise gate that utilizes the LM1894 noise control chip. You can still get the chip off eBay and the SMD version is available from Arrow, Mouser, etc. You can wire it for true bypass or if you want buffered bypass that option is available as well. Should work in either a 1590B or 125B. Schematic for reference.