In 1974, Switzerland put 140 M109s into service under the designation Panzerhaubitze 66. A further 437 vehicles followed in several delivery batches up to 1988. All vehicles were gradually upgraded to the M109A1B armour status.
In the period 1996-1998, 108 Pz Hb 66/74s underwent an overhaul of the electrical system.
(SELAN = renovation of the electrical system)

The Pz Hb M109 (M+76068) is stationed in Altstaetten.