DIN (Deutsches Institut fur Normung ) specifications for application coding of lubricants proceeded ISO 6743 coding.   The lubricant coding references by application are in different DIN specifications unlike ISO 6743 which uses subsections of ISO 6743.  Some of these DIN specifications for coding references include:

            51 502 for code H (hydraulics)

51 503 for code GK, formerly code KA or KC (refrigerant compressors)

51 506 for code V (air compressor lubricants)

51 517 (parts 1,2 and 3) for code C (gear oils)

51 522 for code Q (heat transfer oils)

51 524 (parts 1 & 2) for code H (hydraulics)