I've seen a lot of 1960s and 70s homes in Ireland where boxes arn't really used. The wall plates are mounted onto plasterboard (drywall) usually a fairly substantial cavity and they just use like 3 inch or more long screws to hold it in place there are cable grips on the back of the plates though and they're usually carried in plastic conduit to the fitting. Boxes are absolutely required now, not sure if they were then too but there certainly are lots of them done that way!
Solid walls usually have conduit burried into the sub-plaster work (usually plastic)
In some houses dating from the 1930's & 40's where Schuko fittings were originally used the quality of wiring and workmanship is FAR higher than today.
All cables including in the attic space are carried in sealed black round metal grounded conduits fixed very neatly to the joists. You see no cables at all it looks like very neat plumbing.
No rings,10A, 12A or 16A circuits lots of Diazed fuses usually a very large black distribution board. or in some cases the fuses are in each room mounted over the door on a small black plate with a cover.
What ever specs they were following they were very high!
The sockets tended to be flush fitted into the skirting boards or onto wooden panneling (round fittings) all grounded, have never seen an ungrounded one. Very neat round flat usually dark coloured recessed socket. Where they're on a wall they're usually mounted in a circular carved wooden backing plate like an old lightswitch.
Switches were simple or ornate round brass tumblers mounted on round carved wooden plates (many of these still in use just rewired to remove old cabling)
Many of these installations were updated simply by replacing the cables in the conduits and fitting BS1363 outlets (much larger and uglier) and adding a modern distribution board and RCDs... All on radial circuits though.
I suspect that these installations were actually either done or certainly approved by the ESB (Electricity Supply Board) itself as the standard of workmanship is way beyond anything done in later periods or earlier.
Where BS546 was used in the 50's and early 60s the wiring is much less "organised".
Eventually all the above was replaced by BS1363 13Amp sockets & ring circuits.
