A question about the codes on capacitors

[Nightmonkeyii]

hi all,

Just curious about the first row on the capacitors that ill be replacing on a number of my macs. Ive noted everything down. For example, The 47uf 16v seems to be common, and on all macines measure 6.55mm, measured with a digital vernier. But the first row varies on each machine. The iisi is b4, lciii is 2t. 580cd is f4 and classic ii is 2u. What does it mean?

 

[cheesestraws]

Wild guess: it might be a date code?  I believe the Japanese standard date coding for SMD components uses lowercase letters...

 

[Nightmonkeyii]

I didnt think it had any real value, was hoping it wasnt a value multiplier. Cheers cheesestraws