Paul Hynes SR7EHD-21/27 Power supply with umbilical cable. Set for 27V but can be internally adjusted to 21V I believe, although I have no idea how. The cable has a small nick it the casing of one core where the conductor cable has tarnished/oxidised, although it might just be paint, as shown in the photos, which I hadn't noticed until uninstallation. 3 Sorbothane feet included.
The internal regs are:
TDR21 dual 21 volt regulator module
S1709v4LN regulator module
Z1705LN regulator module
I've got installation instructions I can share, and I'm happy to help with installation if I can.
Prices are:
SR7: £325 + £15 UK shipping
Internal regs: £120 + £5 UK shipping
Buy both for: £425 + £15 UK shipping
Collection from Leeds welcome.