State of Charge for Cal/Cal battery

A mate has just purchased a new camper trailer with two of the Exide ???????Stowaway Leisure Cycle ST27DC95 batteries installed. As a short term measure, I suggested installing a digital voltmeter to give some idea as to the SOC of the batteries. I am trying to track down the SOC voltages for this type of battery.

Are they any different to the SOC voltages of other type of batteries?

I realise these voltages can be subject to the "rest" state of the battery.

I have logged a call with Exide's service desk, but unfortunately the issue is unresolved.

Thanks for any assistance that can be offered.

Brian