I'm beginning to suspect that the French don't have small glasses of beer for pacing, temperature, and economy, but because they don't have a reliable word for a 50cl glass.
In the UK a 'half' and a 'pint' are standard. You can walk into any pub and ask for a pint of beer and while you may be queried on what sort of beer you want, there will be no doubt about the quantity.
In France, you can ask for a chope, pinte, grande, double, serieux, demi-litre, and you will always cause a wee frisson of consternation in whoever's serving you, who will then (even if they find it plausible) require confirmation (with sizing gestures). If you ask for a pinte they will ask if you mean a chope, and if you ask for a chope they will ask if you mean a pinte - or any other combo.
Of course, if the establishment is frequented by clientele who often order a 50cl quantity, then there'll rarely be a problem, but away from the tourist zones, out in the sticks, there will be.
I used to think it was a matter of pronunciation, and that one day, like Kwai Chang Caine, I'd have mastered the art of ordering une pinte, but now, in defeat (or zen-like enlightenment), I've resigned myself to 'Une bière' or 'Une pression', and having to put up with having to order them twice as frequently.
Has anyone else come across this issue? Does there exist a way of ordering a 50cl beer that works, sans hésitation, in every bar in France?