The BJP - Crawley - Dilute DK50 uses additional Metaborate to maintain it's activity at 1+4 and keep development times within reasonable parameters. Crawley published this version of the formula Jan 27th 1961 in the BJP, the Metaborate solution is given as 10z in 12oz water, (83.3g/litre), same as the 1976 BJP Annual version I gave above.