Black Diamond
Pearabiner (1990+) v1

Made from relatively small 10mm rod stock, this is a classic belay/HMS style carabiner, with a coarsely threaded hinge-stopped screw lock gate. The sleeve unlocks with a single full rotation, and is formed from a thin-walled tube. Combined with the hinge lock, I can't imagine this would offer much gate face resistance against hardware roll-out or foreign objects. This thin gate plus a 1800kg (4000 lbs) rating highlights how expectations of carabiner strengths have changed over the years.

Cleverly, manufacturing the locking sleeve does not require internal threading. The thin-walled tube is dimpled in two places which rides loosely along the gate threads. Unfortunately from the user's perspective, it creates a loose fit between the sleeve and the gate, which easily unscrews under vibration - especially bad considering the coarse threading and the orientation of this carabiner at top belays.

From examining the display at the Karabin Climbing Museum, this is similar to the 1990 model of the Chouinard Pearbiner but has Black Diamond stamping. When the Chouinard Equipment Company entered bankruptcy in 1989, a group of former employees purchased the assets and incorporated as Black Diamond Equipment.

This example has the Black Diamond name, but retains the original BD logo: a C (for Chouinard) inside a diamond. (BD would later stylize the C as a sharp angle, creating the modern diamond-inside-a-diamond logo)

The retailer Mountain Gear listed a BD pearabiner at $9.95 in 1992, noting the MSRP was $13.95. The advertisement, however, did not have a photo and I cannot for sure say if that is the same model as shown here, or a slightly different version.