Candlestick Silver or Plate? Can't figure it out

Please help, I can’t read this hallmark for the life of me, none of the obvious marks seem to be there but I thought plate didn’t have hallmarks like this.

Could any of you help shed some light on the mark as I desperately want to give it a good clean but am worried I will use the wrong stuff on it. I apologise if I am being extremely ignorant but I just want to do right by the candlestick as it is rather pretty.

Thankyou.
Candlestick2.jpg
Candlestick.jpg

I think the ISG could be Israel Sigmund Greenburg for Birmingham or Sheffield but I can’t identify a city mark to match either of them. As for the Gothic P that would be 1889 if I was right in my birmigham guess… can any experts shed light for me

Yes, ISG is Israel Sigmund Greenberg, but the other letters are EP and NS which of course stand for electroplated nickel silver. To clean use the same sort of silver polish as you would for solid silver - the surface is silver, but it’s only very thin so you must be careful not to overpolish or you might expose the base metal