PM or P.M. stands for PlusMinus (see below) but also for Past Moves, and Perpetuum Mobile.

Originally active from 1978 to 1984 as Nasmak. All members, including De Groot, have since worked together in partial formations. As a collective they created Nasmak PM (PlusMinus) in 2018.
PM mainly stands for PlusMinus, to indicate that the line-up is variable and it is not just about the old Nasmak: members have left, or are sometimes unavailable, and there is also a desire to be able to work with guests.
Nasmak PM started 40 years after the founding of Nasmak by Joop, Henk and Toon.

PM1 Perpetuum Moblie: “[m=3384664]” (2023) is the first album of this renewed collaboration. It is called Perpetuum Mobile, because the 9 tracks on it are related to material from the early Nasmak days.