The upside is though, while sat at the laptop, I did some furkling and managed to identify dad's Longines. Looks like a late 50s / early 60s stainless steel-cased calibre 30L - though can't confirm that 100% without opening it up.
I always remember him having it, but he never wore it because it had stopped working - he had a cheapo quartz chronograph instead. He must have done BITD though, because the caseback is quite scuffed and the strap is definitely a replacement. He got it serviced a couple of years or so before he died, and I certainly won't forget the temper tantrum at the cost.
Having said that, I'm not happy with the work that was done. It's got a badly-fitting replacement crystal (it fell out and dropped onto the floor the last time I wore it), a very chunky replacement brass crown, and a stem that's much too long and protrudes from the case. It works and keeps good time, but I get the feeling dad went for the cheapest option when it came to parts.
I first need to get grandad Arthur's Tissot tank mended (the mainspring has snapped / come adrift) and then I'll see what my watchmaker can make of this one. Trimming the stem and fitting a much flatter / thinner crown should make it much easier to wear, although at 34mm, it's bigger than I'd want to go.
Anyways, time for a

and a yum yum.