A pub general manager has explained what the number means on a pint glass - and clearly it was quite the revelation for many.
While it's safe to say that the majority of us are too focused on drinking what's inside the pint glass to notice any numbers, it turns out that there's a reason behind them being there.
'Pub Man Dan' said in his 2021 video: "If you've ever wondered why your beer doesn't look quite right, you see those bubbles forming on the side of your glass, it's because of that number there... That's the year the glass was made."
He continued: "You shouldn't keep your glasses for more than three years, after that three years, you should be getting rid of them and getting new ones."
The clip has been viewed almost 200,000 times at the time of writing, with many viewers running to check out their glasses.
However, lots of people also disputed some of his claims.
He's not wrong that the number denotes the year the glass was made and CE marked - which indicates that it complies with serving directives and health and safety requirements.
But many people argued that the bubbles on the side of a glass stem from dirt and can be removed by using glass cleaner.
You've no doubt had a pint before and noticed tiny bubbles lining the walls of your glass - while your mate's is all clear. This is a bad thing.
"A head of foam on the top of a beer is ideal; however bubbles forming on the sides or bottom of the beer glass and then rising to the top may indicate the glass is not 'beer clean'," explained beer dispensing equipment supplier Micro Matic on its website.
"Bubbles form at the sides and bottom of a glass, where residue or microscopic cracks serve as starting points for carbon dioxide molecules to gather.
"When the carbon dioxide at a collection site reaches critical volume, a bubble detaches from the glass and launches itself toward the beer's head.
"A clean beer glass should not have bubbles anywhere but in the head on top of the beer, or lacing on the side of the beer glass."
Lacing is the residue left by the foamy head on the inside of the glass as you quaff it down - but if you spot those pesky bubbles on the side of your pint when it's full, send it back. Or just knock it back if you don't mind a bit of grime.
Don't worry if it's all suspiciously gathered around a logo though - that's probably not dirt.
Micro Matic continued: "An exception to this is laser etched glassware. Brewers are now marketing glasses where a logo or insignia is laser engraved into the bottom of the glass.
"This forces bubbles to form around the etching, highlighting the Brewer's logo. Eventually the bubbles grow large enough to rise to the top of the glass helping to maintain the head of foam.
"This is done to enhance the beer drinking experience and to differentiate the beer brand."Featured Image Credit: TikTok/@pubmandan