The auctions are open to everyone: individuals, professionals, public associations or bodies.
For some sales, participation criteria may be required for legal or security reasons (hazardous materials, etc.). Everyone is free to make a bid on a product of interest.
Some sales are restricted to authorised professionals (e.g. rolling stock merchant), in which case this will be stated with the header " Sale reserved for trade professionals ".
This is requested by certain vendors due to the guarantees on the material sold.