Thank you, I will.
You may be right about that we have something like USDA. I'll certainly check. What I do know is that pressure canning is not a big thing here. We do a lot of water bath canning of course- jams etc but not pressure canning.
If I can't get any answers here, I'll just have to experiment. It shouldn't be too difficult to see if the seal is OK or not. Probably just a matter of releasing the spring-lock and see if the glass lid remains fastened. That's my theory at least