Any #brompton experts here?

I was folding my (P line) Brompton the other day and heard a small "ping" sound. Then I saw this small, black, anodized, Phillips-head screw on the ground - but I can't find where it fell off from!

Anyone have any ideas?

The bike still works fine, at the moment: it gets me around the streets of Pisa quickly and comfortably, easily on the train even when crowded, even up&down the 4km long, 350m high hill near my house -- a reliable companion!

Thanks so much for all the suggestions here!

I actually don't have access to the bike for the next 16 hours, so I can't follow up immediately. But tomorrow AM I'll check and post what I find, in case anyone is curious.

@poritzj uhh, tough one. did you check the front luggage rack block? the mudguard holders? and the chaintensioner components?
@poritzj Could it be one of the screws which hold the brakes pads in place?
@poritzj End of the pedal would be my first guess.
@poritzj could be FOD on the road. But check the rubber mudguard flap, they are fixed with two screws like that on mine.
@poritzj It looks like a shear, as in half the bolt is still in there and from the ping sound that is likely the case. So did you tighten or have someone tighten something recently, I'm thinking saddle area or folding hinge.
@byrnensorg I don't know, the bolt doesn't look broken...
@poritzj for holding the rubber seatpost bung in place?

@tlohde @poritzj Rubber insert on seatpost is a hex-screw on older Bromptons, on newer Bromptons there is no screw any more.

Lost the new pung recently (which is significantly lighter than the old one) and put the old one on again, hence I know. 🥴

@poritzj is it from the brake levers ?
@quixoticgeek @poritzj That would be my first guess, somewhere from the things mounted on the handlebar. Or mudguard fixtures. 🤔
@poritzj I would look at the mudguard stays first. Could also be the shifters, maybe.