Dating Old Electrics

Some dates - but may contain errors, and sometimes things did get installed later than they should strictly have been.

(If you grab that wooden adaptor, you do indeed get hold of live tubes that come very close to the surface.)

Lead sheath cable: some say before 1948, some say it was still being installed in the 50s. On farms it was used in the 60s.
TRS (Tough Rubber Sheath) 1945-1962
Capothene (rubber insulated, polythene sheath): 1952-1960
Ashothene cable: 1952 - 1960
PVC inner PVC outer T&E style cables with no cpc (no earth wire) (lighting circuits): 1955-1966
Imperial PVC cables: 1955 - 1971
2.5mm² PVC/PVC T&E with 1mm² cpc: 1971 - 1981
Twin twisted flexible cords: before 1977
Single insulated figure of 8 speaker type flex used as mains lead: until 1976 in UK
Rubber/PVC mix T&E cable: 1958 to 1961
CMA (Cable manufacturers association) cable: ceased in the 1940s
Non-association (Nonazo) cable: pre apx 1948
Aluminium cable: popularish in the 1950s, and to a lesser extent the 1970s
Copper clad Aluminium cable:
Maconite cable (very distinctive O--O shape): pre WW2
One you'll probably never see: very thick bare soft iron wire, used from late 1800s to 1920s on 32v generator powered lighting systems. System shown in the 1945 Agatha Christie film 'And then there were none'
White insulated conductors: until 1966

Separate bare copper earth wires run alongside twin cable: 1960s and earlier
Black earth conductors: before 1966
Green protective sleeving: before 1977
Green & yellow earth sleeving: 1976 onwards - 2nd ammendment (1 April 1976) to the 14th edition regs stated "The use of green alone as the colour identification of earthing coductors is admissable until 31 December 1977, after which the use of this colour may no longer be described as complying with these Regulations"
Earth wires just twisted together at junctions: still common practice in the 70s

Dates aren't especially accurate yet in this section

Cables fixed to wall with ceramic cleats (small plates with grooves to hold the wire): pre WW1
Wooden trunking:
Rubber singles in steel trunking: popular in 1950s, most likely used in early 1960s too
Uninsulated metal cable clips/cleats: still in use in the 70s
Homemade junction boxes, typically a tobacco tin: pre-war

This refers to the main bond between electricity incomer and water/gas/oil incomers, nothing to do with bathroom equipotential bonding.

The dates here don't provide much certainty when dating an installation, as lots of houses were rewired later without updating the main bond.

ELCB (Voltage operated circuit breaker): pre 1981
Double pole fused switchgear on ac Installations: pre 1955
Wood backed Wylex fuseboxes: still being installed in 1983
Slate fuseboard with bare screws for fusewire links: in use in late 1800s, obsolete by the 1930s
Wooden fusebox with wooden lid: standard in 1930s
non-EEBAD installs (local earth rod but no ELCB or RCD): pre 1955
Assorted switchfuses rather than 1 or 2 fuseboxes: until 1960s
Ironclad fusebox & plastic version of: likely pre-war in domestic installs

Accessories mounted on wooden pattress blocks: before 1966
Round pin socket outlets (BS546 3 pin): mostly before 1955, but sometimes used much later, as in this example feeding a small transformer (the Clang adapter is old, and as it has unshuttered sockets shouldn't be used domestically)
File:2amp3pinclangadapter
Square pin 13A sockets: post 1945 - may be on older wiring though
2 pin 5A round pin sockets to BS372 (excluding bathroom shaver sockets, which are still in use): 1928 to 1930s, but also used later
No sockets upstairs, or just 1 in corridor: typical 1930s practice. Exactly when this ceased the author doesn't know, most likely 1946 or 1947, but may be earlier
Sockets with no shutters:
D&S round pin 13A plugs/sockets, where the live pin is a fuse: 1940s on, some still in use in the 1980s

Plugs

Sometimes plugs can help date an appliance, but of course they were often reused and replaced.