British Standards Document
BS EN ISO 2503
Gas welding equipment. Pressure regulators and pressure regulators with flow-metering devices for gas cylinders used in welding, cutting and allied processes up to 300 bar (30 MPa)

https://doi.org/10.3403/30171725U

BS EN ISO 2503 is maintained by WEE/18. The current release of this standard is:

BS EN ISO 2503:2009+A1:2015 Gas welding equipment. Pressure regulators and pressure regulators with flow-metering devices for gas cylinders used in welding, cutting and allied processes up to 300 bar (30 MPa)

https://doi.org/10.3403/30171725 (published 30/09/2009)

This standard is available from the following sources:

Other historical versions of this standard document also exist:

BS EN ISO 2503:2009 [current until 31/05/2015]
BS EN ISO 2503:1998 [current until 30/09/2009]