Large Japanese Singing Bowl, Signed: Age, Maker?

I got this about 15 years ago in Astoria, Oregon, at Phog Bounders Antique Mall. At the time I didn't realize it would sing when stroked; I just thought it was a beautifully done piece of hammered brass or bronze. I use the word 'sing' in the conventional sense that many, usually smaller an' shallower, bright, an' more openly shaped bowls. often from Himalayan nations, will sing when properly handled. This one Howls with a deep, low growl which sustains for long an' long after stroking ceases. I hadn't seen the 2-character signature until after I dusted it, though I was pretty sure it was Japanese...an' I can only hope it's got some good age to it.
The underside of the rim is smoothly built up, perhaps with bronze, but possibly tin or another base metal; I believe the purpose of that inside 'filet' is to tune the bowl's tone, somehow; it's very difficult to photograph that area.
It's ~7" high, 10" rim diameter; weight is 3 lbs 4 oz.
All your comments an' observations are most welcome...Thanks for lookin'!