This is a basic device based on a TigerJet 560 (there's documention online for the 560B, but it has the advantage of presenting DTMF decoding as a USB HID, rather than requiring querying). I think it was going to be marketted as a "Wildcard S100U USB FXS Interface", but I can't find any sign that Digium ever shipped these properly. There's a mailing list post from Mark Spencer that says they were too flaky to put their names to. An lsub shows:

Bus 001 Device 004: ID 06e6:831c Tiger Jet Network, Inc.

I bought this off eBay ages ago, believing it would be supported under Linux by Asterisk due to the existance of the Zaptel wcusb driver. However this turned out not to work under 2.6 and apparently doesn't even work under recent 2.4 kernels.

Andrey Schmiegelow pointed me at the tjnet driver from TigerJet themselves, but it only did device setup and not any audio. However, the device presents USB audio endpoints, so I used the tjnet driver as a basis for a userspace util that can do all the setup required to make audio work using the stock kernel USB audio driver. You can download this tool, tjctl, from here (v0.0.1, 14k).