The 6N, sporting an old Audiodisc for show and an aluminium Audiodisc swarf brush. No. 2374.

Left, an early K - no numerical designation and only able to cut I/O. Right, a later K8. Both need re-capping and I suspect the K needs new transformers as well.

Heads:
Audax H4
Presto 5C (repair underway)
Presto 1-D (in so many pieces)