i seem to remember that they were part of a non shimano pedal but that is similar to the pdm324 from shimano, meaning they are traditional style pedals with a spd on one side but the pics you have there are the removable spd part without the rest of the pedal. does that make sense? think the brand was "acor"
They look like they might fit Wellgo pedals. Some bikes we sell have caged pedals on them that have a recess in the centre that is designed for this sort of thing.
Never thought I'd see the day when you could get them separately though.