Not sure if its changed, but gliders had an exemption that allowed them to omit the first letter of the rego..
I.e my favourite bus (being my first Single Seater) only carried the letters IF. Full rego was VH-GIF
I later flew VH-XOC and XOB.. they also only carried the last two letters as identifiers.
It was extremely unsafe by todays standards, but i survived.
I've said it before, and i will say it again, until the industry stands up as one against this muppetry, the doom will continue to increase.