Well it's a Continental RVMA 6V25. I ordered it brand-new for a different project years ago and never used it. According to the datasheet, it has built-in PWM including logic to ensure it switches at the zero-crossing point.
The problem is it doesn't work. I hooked up a 5V PSU with a 1kOhm pot+250Ohms which should give 4-20ma. However the light never comes on on the SSR and it shows 5.00 volts across the inputs, like no current is flowing at all. This is pretty strange, because I expect a current input to be very low-impedence, but it's acting like it's dead open.
Also strange is that when I plug a CFL light into the 120V outlet between the SSR'd phase and neutral, the light comes on at seemingly normal brightness. However, when I plug my heating element in across both phases, it does not seem to heat up, even though I measure 240V at the plug. So it's like the SSR has 'failed closed', but will only supply a few watts. On the other hand maybe the CFL is 'off' but the CFL is running off the leakage current.
This is a killer because I wanted to brew this weekend, and now I have to buy an SSR and make up some kind of PWM.