Thanks. I'd found similar.
One of the links says
Model Ref:
Model Ref:3748420 "274.8.85" so I'm not really sure what the 374 number is. I don't think that's a JLC model no but I could be wrong and googling it does get you to 986 models.
ETA
Ok it seems there was a limited edition of 1500
https://www.europeanwatch.com/19356.html
and the same piece but not in that 1500 run
https://www.swisswatchexpo.com/watch...Q3748420-11570
broadly they are 44.5mm by 31.5mm but it does seem to vary by a mm or so.
I can't see what value there is in the 1500 run mind.
And again - the limited 1500 are 274.8.85 but the others are 273.8.85