Help with calculating pension entitlements - public sector worker

"To be eligible to make voluntary contributions you must:

• Have at least 520 PRSI contributions paid under compulsory insurance in either employment or self-employment"

Does this mean 520 paid contributions at any class (eg A, D, S) OR 520 of the relevant class ?
(The most recent class would then determine which class you can buy)

Also, one thing to bear in mind - only 260 contributions can be voluntary.

Trying to track down official confirmation of my wifes 10 years in a hospital is like pulling teeth.

We eventually found a contact person in their superannuation dept who deals with these specific queries.
2 phone calls, 2 months apart- 'sorry, she's away...'
1 phone call - contact made ! However she works half-days only, Mon to Thursday.

She said she would find out my wifes pension/service entitlements - that was 3 weeks ago...

... tumble-weed.....