Pretty sure this is sensor for a WEMA system with a 400 mm rod. Visually check out this site for what you are looking for as they do not list a W2-400 sensor :
Wema UK - Sensors, gauges and displays
OEM of Analogue & digital sensors, gauges & multi-function displays. Senders & engine monitoring kit for marine, automotive, industrial, military & agriculture
wema.co.uk