I've arrived late into this intriguing coversation, but, my observation may be of interest.
As you have correctly been advised the marks you've noted are merely dividers; the reason you consider them as quotation marks may be down to the limitations of A.S.C.I. code ~ there's not one for the sterling currency divider markers.
We used double dots, side by side, but NOT placed on the line; they were placed halfway up the height of the numerals. I have a vague recollection of that particular lesson, to this very day. [ Mrs. Stratton, I believe.]
Of interest, may be the treatment, in Britain, of the decimal point. We place the decimal point midway up the height of the numerals. On 'the continent', [Europe b.t.w.] they use a 'comma' thus:[ , ] placed upon the line, to divide the units from the tenths.
That took me a while to get accustomed to.
I'd return to the old method in a heartbeat, if it were my decision. But that's just me.