Hi all. 
Trying to identify what part this is.  I'm ok on mechanics but electrics,  not my forté.  Any help appreciated

Is it a starter motor relay?

I see this is your first post, it's worth introducing yourself in the Newbie section, what you got, whereabouts are you etc

All the best and welcome
Dave

Looks like a universal solenoid for a starter motor

If not a starter solenoid switch if there is a key tube the other side it may be an isolator switch with bypass for alarm/ radio power. non standard so could be removed unless there is a small light weight starter switch.

Looks like a universal solenoid for a starter motor

Indeed it is - a lot of the older classic cars ad them before Lucas started bolting them to the side of the starter motors 

If it's on a buggy it's probably been wired in as a 'hard start' relay.

Thanks all
How do I find out if it's a starter relay or a battery isolator?  Take it off and see if it starts?
I will also post in the newbie section and say hello
Cheers

try googling   LUCAS SRB325

The hot start relay set up was used to overcome problems with voltage drop on early beetles and poor ignition switches on later cars it just means the power to engage the starter solenoid is done through a relay to take the load off the ignition switch.
The solenoid you have is serious over kill that was designed to run the main battery power to the bendix type starter motor before pre-engaged starter motors became the normal item on cars.
With good wiring you will not need it unless you use a low current  ignition switch.