This Decca boxes have come from other sources, like the Gulda Amadeo that showed up it awhile back. I don't think that Guarneri recorded more than one cycle, so the two are probably one in the same.
Actually, George, the Guarneri recorded two separate cycles. Here is the Guarneri for RCA in the 60's:

...and here is the Guarneri for Philips (Polygram)
in the 80's-90's.