Mystery object (B62 near Blackheath)

Does anyone know what this is? And can you make use of it? I’ve opened the packet, it’s unused but dirty due to years in the shed.

2 metal bits pos legs, bolts, plastic seat shaped item and fittings that include pins and pos axle holders.

If you want a puzzle or If you can make use of these plesae let me know when you can collect from B62 near Blackheath