A type of toggle clamp: https://www.mcmaster.com/products/c...-action~pull-only/pliers-style-toggle-clamps/
Never seen that,, but,, I should like to try them for mounting tires on the clincher rim. Would make it easy to get the bead onto ( into ) the rim.
DE-STA-CO clamps.... As 2FORSEFULL, said missing the bolt.... Bolt had a swivel foot and a jam nut on it.... I still have a few of them.... use one every so often.... LynnW
They've been making them since 1936, this style is called a 'squeeze action clamp'. https://www.destaco.com/clamping/manual/squeeze-action-clamps.html