Hi Juvela - hadn't checked the forum for a little while - I see there's been a lot more sleuthing! Thank you! The Agrati "Corsa" series is handsome indeed.
For the frame I think we could safely conclude Atala at this point. I wonder if anyone will ever remember what the "LA" means. I did lots of internet searches, but no dice.
Here are the fork measurements: pitch 1.0 (at least that's the only one that made any sense at all), OD of the threaded tube : 25.5 mm. ID of 22 mm.
Thank you, again. It's been a very interesting education for me - how many different manufacturers come together to make a bicycle!