Does anybody know the identity of the Track machine parked north of Upminster station platforms

I viewed it on the incoming service from Romford but headed south towards Barking on another service so did not get the id.

Many thanks in advance.

To be honest I saw it on Wednesday morning and have since forgotten !!!

Thinking about it now , I think it was a Balfour Beatty blue and white track machine.

6j13 (should be 73906) worked in from Grays on the 13th. Then on the 16th something went to Broxbourne but the headcode doesn’t show.

Thanks for the reply, appreciated.