PolyGram Record Services Limited (PolyGram Record Operations Ltd.), operating between February 1979 and mid 1988.
Manufacturer and distributor with a vinyl pressing plant located in Chingford/Walthamstow, Greater London.
The plant operated under this name from 2 February 1979 (registered 11 May 1979) until mid 1988 and then closed down.
Succeeded Phonodisc Ltd. and was integrated in PolyGram Record Operations on 1 January 1980.

PRS manufactured injection moulded 7"s for the UK market for the Philips and Polydor families of labels. Usually, those singles carry Made in England on the labels and have a small spindle hole within a wide black ring. PRS also produced already dinked 45s (as did Phonodisc Ltd.); these titles require separate entries in the database distinguishing them from the solid centre editions.

Lacquer cuts can usually be identified by "// x ▽420" found stamped into the runout area of vinyl releases. There are occasional exceptions to that rule though: sometimes the ▽ or the "420" may be omitted or replaced by letters, or the two forward slashes may be missing. The letter "E" combined with "420" means the record was cut in-house (e.g. "// 3 ▽ E420").
Being a full service provider, the records were normally also pressed there - for exceptions, see below.

Because PRS Ltd. only had two lathes, it was common to outsource the lacquer cutting to other studios. At first external cuts were marked with "▽E" + additional letters, signifying the respective cutting studio:
▽E AR = Abbey Road Studios
▽E C = CBS Studios, London
▽E D = Decca Studios - until 1980
▽E IB = I.B.C. Studios
▽E JVC = JVC Cutting Center
▽E KR = Kendun Recorders
▽E M = Master Room
▽E MC = Music Centre, Wembley
▽E MCR = Master Cutting Room
▽E MD = Masterdisk
▽E ML = The Mastering Lab
▽E P = Pye Studios - until 1980
▽E P = PRT Studios - after 1980
▽E PS = Portland Studios
▽E R = RCA Studios, London
▽E SC = The Sound Clinic
▽E ST = Sterling Sound
▽E STR = Strawberry Mastering
▽E T = Trident Studios
▽E TH = The Town House
▽E TO = Tape One
▽E USA = Lacquer cut was done by a studio in the US
▽E UT = Utopia Studios.

The identifiers for external lacquer cuts were still in 1979 changed to "▽420" + 1 additional letter (“▽130” for US studios). The letter signifies the respective cutting studio:
▽420 A = Abbey Road Studios
▽420 C = CBS Studios, London
▽420 DEC = Decca Studios
▽420 E = EMI Studios or (The Penthouse, when explicitly stated)
▽420 EX = The Exchange
▽420 G = Portland Studios
▽420 H = The Town House
▽420 J = JVC Cutting Center
▽420 K = Kendun Recorders
▽420 L = Dublin Disc Cutting Service
▽420 M = Master Room
▽420 MU = Masterdisk USA
▽420 P = PRT Studios
▽420 R = Master Room
▽420 S = Strawberry Mastering - until 1983
▽420 S = CTS Studios - after 1983
▽420 T = Tape One
▽420 U = Utopia Studios
▽420 V = Trident Studios - until 1985
▽420 V = Audio One - after 1985
▽420 W = The Music Centre, Wembley
▽420 Z = The Sound Clinic
▽130 = Lacquer cut was done in the US, usually by Masterdisk or Sterling Sound
▽130 SS = Sterling Sound

Contract pressings:
▽420 DA = Lacquer Cut At PRS Ltd. and Pressed By Damont
▽420 FRA or ▽420 FRA POLYGRAM = Lacquer Cut At PRS Ltd. and Pressed By Polygram Industries Messageries, France
▽420 MSL = Lacquer Cut At PRS Ltd. and Pressed By Multiple Sound Pressings Ltd., Leicester
▽420 ORL or ORLAKE = Lacquer Cut At PRS Ltd. and Pressed By Orlake Records
▽420 WEA = Lacquer Cut At PRS Ltd. and Pressed By WEA Records Pressing Plant, West Drayton