I had looked into Filmotype’s range and ruled it out, because Stuart Sandler (the publisher of the digital versions who acquired the Filmotype assets and researched the history) dates Marlette to the “late 1960s” and Mansfield to the “mid-1970s”.
Attached is a comparison using three glyphs from the orginal Marlette as shown in a c.1974 specimen, which I scaled and (uniformly) stretched to match the cover typography as close as possible. None of them is a cigar: in Marlette, E has a higher (and bolder) middle bar. In N, the weight distribution is different, and the modulation in S is off as well.
I understand that you, Kevin, are not claiming that the Filmotype faces are a match (you’d then posted it as an answer, not a comment). But it’s good that you bring it up: I agree that those fonts are the best digitally available option for recreating the covers!
As for the actual ID: there were more type providers active in the United States in the 1950s and 1960s, apart from the usual suspects such as PLINC, Filmotype, Headliners. Lettering Inc. is one such candidate, and there probably were others – short-lived or regionally active ones – too. From the limited material I’ve seen for Lettering Inc., Filmotype & co. might have adopted some of their designs, directly or indirectly. If the album cover isn’t hand-lettered, then it could use such a typeface of unknown origin which possibly served as model for Marlette etc. at a later point.
