- Shown in the slider are four different custom covers used by Philips in 1951-52 (possibly early 1953). #2 and #3 are similar.
- The order in which the covers are shown, is correct. The black covers came first and were f.i. used for the very first Philips albums: 10 inch album A 00111 R and 12 inch album A 00110 L. It seems that this first cover always came as a gatefold. The first blue cover version was gatefold too, at least sometimes. After that the gatefold format was dropped for standard LP releases. The gray cover came last, but all of these covers have been used concurrently as well. Possibly the gray cover was used for new releases, where the blue one was used for reissues. Incidentally the black cover was also used for reissues (maybe from leftover stock).
- Another thing worth investigating is if all early A numbers (like A 00133 L) were issued in a black cover first. The A indicated a more expensive release than the N, but remained in use for reissues (with blue covers). The gray cover variant seems to always show the A as the first character in the catalog number.
- All of these have been used for both the 10 inch and the 12 inch format.
- Note that the covers all have unboxed speed designations, though the labels often show the later, boxed variant. The unboxed speed designation was used on the labels until c. mid 1952 (June?), but it seems there are a few exceptions too. In these early years Philips also started reissuing their titles, meaning all kinds of combinations are possible.