Was it...

Same As the US Silver Certificate?

If not then what was this silver part about?

I believe so, older paper money was usually backed by things like gold and silver, occassionally the notes themselves would reference this while some didn't.

Country was running on silver/bimetal standard. Up until 1867 all silver circulation coins had full silver value in them.

You could go to state bank and exchange that credit note for 50 silver rubles. 900 grams of fine silver. No questions asked. No paperwork demanding to explain why you ask state to give you its silver/gold reserves.

These notes were substitutes for coinage in circulation, and as such, you got real silver coin in payment! An age when h`rd currency had real meaning - valuta.