How would i tell the difference sir?
The little lever should have "M" on one side, "N" on the other. Two "M"s or double "Lp" notation means its microgroove only - type (c)
The jewel (needle tip) furthest from the cantilever tip (the "N" needle) is always a sapphire, and you can see it has a glass-like crystal nature throughout. If both jewels look like that, it is a double sapphire - type (a)
However, if the end-most jewel (the "M" needle) is a really tiny speck of black, attached to a small brass mounting, which is in turn glued to the cantilever, then that is a diamond type (type b).
(NB, these a, b c assignments are just from my list, not a Philips notation)
