supply of cut off angle cock with vent for air brake coaches to rdso drg no-wd-88123-s-01 alt. 2, and part rdso drg.no.wd-88123-s-02 alt.-6, conforming to rdso specn. no. 02-abr-2002, read to all amendment with latest amendment no. 4 of sept. 2016. appendix-d.