One of the first references I have found pertaining to the mid-series "white front" & gray back glossies came from SCD in their discussion with John Rumierz on refuting their Canadian origin. John was collecting '52 Topps back in the '70's & noted the difference between normal gray backs & the ones with glossy fronts.
The link follows - see item #6, half way down:
http://www.sportscollectorsdigest.com/topps_canadian/
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