Shaded dogs are the RCA LPs with a SHADED BACKGROUND. (not that the dog itself is shaded!) They are earlier year classical recordings, and are just nice recordings. They generally do command higher prices for the stereo versions. The monaural have no price premium. ALL have 'deep grooves'
The non-classical are just as good, from that period, but because they use a black background for the label, no shading exists, just note the heavier weight of the pressings. (Also for shaded etc, the starting pressing is 1S, closer to 1S the pressing the 'better' and more valuable it is.)
You forgot the Mercury SR90000 series of recordings also are claimed by some to offer better sonics in general, also only the stereo command a price premium. (the monoraul use a # 50000, not 90000. All also 'deep groove'
Then The Columbia six eye. These were made around the same time as the RCA and the Merc, the golden age of LP recording, from 1955 to about 1961 when they used tube recording equipment. Only the non-classical six eye are coveted, as the classical engineers were (apparently idiots)
The problem with the six eye designation, is that much later Columbia LPs have six little eyes too! (a thin ring of the small eyes and the word 'Columbia" alternating evenly around the perimeter of the label), but are NOT the ones called "six eye". The six eye started around ?1954 and have three large eyes in trapaziodial boxes to the right and three to the left of the spindlehole. very striking design. All 'deep groove'ALL the non-classical, Mono and stereo have cachet, Though beware of eBay dealers selling six-eye because some try to sell the much later design as six eye through ignorance or pique.
The six eye are from the golden age 1955 to 1962, and are followed by the two eye, 360 sound label, or MONO, guaranteed high fidelity, all still good.
Deep grooves are just that , the grooves are very deeply pressed into the LP. Later grooves all get very shallow, some barely visible as grooves, they look like scratches on the surface!
Then also the London 'blue backs' with a pale blue background on the back cover..
The ease with which the labels are identifiable has led to the idea of desirablility, ease of finding th style of label, rather than knowing what the preformance is like, has led to a general price premium for these LPs. They are good, generally, but do command a price premium above the actual value of the music on the LPs.
I personally buy them in general, as they DO represent a fine bunch of music, from a great era in recording history,
But just yesterday, passed up a stupid classical recording, London blueback,VG++ at $0.50 because what was recorded on it was not worth fifty cents to me!!
