Numista page for 1 piso coins that include 1975-1978 (https://en.numista.com/catalogue/pieces3748.html) indicate that coins include BSP or FM mintmarks. My coins of these years have no mintmark, matching treatment by Krause 2012 SCWC. Coins of 1979-1982 (KM# 209.2) do have BSP or FM mintmarks. According to Krause BSP did not mint any 1975-1978 coins (1975 were minted by FM (with mintmark), Vereinigte Deutsche Metall (without mintmark) or US Mint (without mintmark); 1976 by US Mint (no mintmark) or FM (with mintmark); 1977 and 1978 with FM mintmark or no mintmark (mint not indicated by Krause). I believe BSP was not open as a mint until 1979 and could not produce coins prior to that date.
In the year list I think indications for BSP mintmarks should be removed from years 1975-1978 and mints as in Krause entered in comments. Coins for 1979-1982 are OK.
Will