Rupes LHR15 bigfoot parts

hi
Do I need a ""serial number"" to verify which speed control suits my MK 1 Lhr15 DA ??. Unit is around 3yrs old . Unit is a 240volt version . Are they the same as the mk1 21mm Da also . Appears as if there are multiple choices for this part when looking at parts diagram . Which parts number is correct ????
Is there a recall for this part as the unit maybe old but done only 2 cars . Part has failed only after very very small amount of work .

Thanks