I planted some lettuce and arugula seeds just under two weeks ago and they seem to have taken. The cold frame is doing its job - even with sub-freezing night temperatures all week. YAY!
(that's my flash drive in the photos for scale)
(I think I'll need to thin the arugula at some point)
No signs of carrot or Swiss chard though, even with the temporary plastic cover I put on the other cold frame :( (though I don't really expect to see carrot seedlings for a while - they're notorious for taking a long time to germinate)