Massey weights

[Banj0Bolt]

I've came across these weights recently through the classifieds, they all fit and will do the job rightly.
I'm intrigued as to which Tractors they might have originally been for.

 

[Adeptandy]

Pic 1 & 3 100 series MF
Pic 2 600 series MF

 

[Banj0Bolt]

The last photo.. Do the long numbers mean anything?

 

[JLLM]

Pic 1 & 3 100 series MF
Pic 2 600 series MF

Would 100 series be in KG ?

 

[d williams]

Looking for a set for 300 series if anyone can help

 

[Adeptandy]

Would 100 series be in KG ?

We went decimal in 72 so I'd have thought possible to be.