Independent label: Neptune Records was no relation to the American company owned by Gamble and Huff.  This particular Neptune label was Scottish; from the look of its few single releases it seems to have had a Scottish Folk / Country slant.  It was handled by Glasgow-based Lismor Records and distributed by Lugton.  Singles were numbered in an NM-0 series; NM-3 was an EP, 'Country Love', by Sheena Easton's one-time husband, Sandi.  The label appears to have been active from 1977.  The highest-numbered single I have seen listed was NM-7, 'Old Scotia's Drum' by Doreen & Country Breeze, which came out in May 1980. Thanks to Robert Lyons For The Info.

77 Fran & Anna Scottish Singalong NEPTUNE NM 1
77 Legend Some Broken Hearts Never Mend NEPTUNE NM 2
77 Sandi Easton  Country Love (Ep) NEPTUNE NM 3
78 Steamboat Row On To Victory NEPTUNE NS 4
78 Don Spencer  What'S A Pommie NEPTUNE NS 5
78 New Ovation Ballard Of Fran & Anna NEPTUNE NS 6
80 Doreen & Country Breeze Old Scotia'S Drum NEPTUNE NS 7