Hi,id say it was a gen 3,cos the upgraded grip doesn't follow the rule of thumb,although it does have finger grooves.its mono slide lock not ambi ,so not gen 5,no back strap.hope thos helps.was about to drop to £70,if still interested.
Nik
We g19.
Wet model with upgraded grip,trigger, ,slide,etc.tan.fibte optic f&r sights.rmr plate.
About month ,never been out of house.
Gas tight mag.
Boxed ,instructions.
£80 incl fees ,postage.