what the heck is this kind of lock??

[Justin Urbantas]

I saw this on an auction site.
The only info was .69 Belgian pistol.
Have you guys seen this before?

[WESTbury]

Never seen one before. The Europeans came up with all sorts of oddities and still do to this day.

Uneducated guess: Some type of self priming mechanism. The screw at the top right of the lock looks to be a hinge screw.

[120RIR]

Perhaps it's some variation on a pill lock?

[Majorjoel]

On some things, when it comes to form vs function.....I'll take form!    That lock makes a fairly nice pistol ugly IMO.

[EC121]

Maybe you work the lever to drop a pellet under the hammer.  That screw at the top right is the pellet holding chamber lid screw.

[Tanselman]

It looks like some gun maker's idea of a [complex] safety device, to prevent acidental discharges. He'd probably seen some of the  German safeties on percussion guns, and thought he could do something better, or at least different, to show off his mechanical abilities. Shelby Gallien

[heinz]

It looks like one of the forms of "pill locks" that used a pill-shaped primer.  They lost out to the percussion cap

[Daryl]

Could have been a tube lock, kinda the same idea as a pill lock - kinda
except the fulminate was contained in a  copper tube.