Ivor, 1970's is a quote from the book '70's is my addition, since many abbreviate the decade that way. Now if a person is in his 70's. there is no ' in front. BUT, see the following.

I looked in the "Harbridge College Handbook" (and found: the 1970's OR the 1970s.
two B's OR 2 Bs
his 7's or his 7s
the VFW's or the VFWs
the &'s or &s

So take your choice. I guess this applies to cd's and cds etc.
Of course, when one submits an article to a journal, their *'archys' will change it according to their predilections.

*'Archy'- The re-incarnated cockroach who typed out "Archy and Mehitabel." for Don Marquis.