It's one of Catalinbread's amp in a box pedals; this one being Tweed Fender. It's raucous, raw and extremely loud. For the first time ever, I feared for my THD speakers.
With the Marshall on 3 and the guitar volume down to 1/2 way it has a fat chime that works very well with a Telecaster. While the amps cleans are good, the F5 adds a woodiness (can't think of any other word for it) that's quite addictive. Open the taps on the guitar and all hell breaks loose.

The volume and gain seem to do similar things with flavour variations. Full volume, no gain is bright and may work best for humbuckers. Pull back the volume and dial in gain and the aforementioned woodiness returns. The tone is usable right across its range. That's a first in my experience.
The sounds here are definitely Oldschool; it's 50's tweed tones after all, but for me this is the one. It's every distortion tone I hear in my head.
I love it, the DLS is on gardening leave and the Cat was last seen dragging a suitcase down the drive.