This is an American's report of late 19th-century Bavarian custom:
"Of the quality of the Bavarian beer, and also of the quantities consumed, I shall speak farther on: I only want to remark in this place that in the measure of the beer one gets there is no humbug. The law requires that each glass and each mug shall bear on its outside the governmental attestation as to its capacity. A horizontal line is ground into the glass or stone showing the exact level which the liquid must have. This line dare not be less than one centimetre (half an inch) from tho rim, so as to allow for the foam. The vessels must be filled to that mark with beer. Woe to the publican who does not come up to the scratch. If, in the hurry of business, such a thing does occasionally happen, the guest is not slow to send his glass back to be properly filled, accompanied with some complimentary German epithets which would more than fill a barrel.
The unit of liquid measure in Germany is, as in France, the litre (something over a quart). Each mug holding that quantity must be stamped with the letter L before the stroke ; if a half-glass, with J L, so that there can be no mistake as to its real capacity. Before the introduction of the new weights and measures, in 1874, the unit for liquids in Bavaria was the mass (the measure), and the stone jugs were marked with an M.
It is so customary to display the initials of the reigning monarch as an emblem all over, as, for instance, on the helmets of the soldiers, on the boxes of the royal opera-house, etc., that one begins to accept the sign as having that meaning only, and no other. An American who stopped at Munich during the palmy days of King Maximilian's reign, and who pursued his studies with greater assiduity at the Royal Court Brewery than at any other institution, returned some ten years later (during which time he had been gathering useful knowledge) when King Ludwig the Second was on the throne. Our friend was not slow in resorting to his favorite place, the Court Brewery. When he got his mug he was at once struck with the alteration of the letter on it. " Well, I'm dod dasted," he said, " if these Bavarians aren't the most loyal people I ever saw,— even on their beer-mugs,—formerly it was always M for Maximilian, and now it's L for Ludwig.""
"Consular Reminiscences" by By G. Henry Horstmann, pages 327-328.
If only every country were as assiduous. Here in Holland pub glasses don't give any clue as to their liquid capacity. And, of course, in Britain short measures are more or less officially sanctioned.
Handy to know when Bavaria went metric. I'd been wondering about that.