Boiler no TPR valve

Older paragon boiler that also makes Domestic HW had no TPR valve.
It is oil fired is this OK?

Is it an open or closed system?

It aPpears to be closed. How can I determine?

I doubt it being a open system, If it is closed what you may have is a bomb waiting to go off. you better make sure it is a open system if not call the owner . this is something not to be second guessing.

Here is some information

An open system will have the expansion tank in the attic.

How about a picture?

open system has a open tank in the system did you happen to see anything like that?

Here is more information

Yep Micheal is right normally in a closet or attic with a over flow pipe , sight glass was normal useless unless maintain . Glen it is very important you follow through on this one

I called the purchaser and sent an e-mail asking owner to have a service professional determine if there is a TPR valve and if not install one immediately.
Thanks for all your help everyone,

Hope this helps.