Are these Indian sterling silver?

[AllSeasons]

I'm thinking of picking up a couple of Indian items, but I'm not sure if they're actually sterling silver. They're marked "S.T. SILVER"; the seller said they were given to him by a wealthy Indian couple. The other mark is "S.A", which I assume to be the maker's mark, but I've never seen this mark before. Does "S.T. SILVER" mean sterling silver? Anyway, I think I'm going to take a risk and pick these up. I may kick myself later, depending on what the forum says. But, you gotta risk it to make it, I guess. Any insights would be greatly appreciated.

The images are below. Thank you in advance!

[amena]

Beware

[AllSeasons]

Beware

Thank you for the reply. Can you please elaborate a bit?

[amena]

It's just a gut feeling.
I have seen a multitude of silverplate marks that look like that, but never a solid silver mark that looks like it.
This is why I would be wary and would like to test it out before buying.
Good luck
Amena

[AllSeasons]

It's just a gut feeling.
I have seen a multitude of silverplate marks that look like that, but never a solid silver mark that looks like it.
This is why I would be wary and would like to test it out before buying.
Good luck
Amena

Thank you for the clarification. That was definitely one of my concerns, as well; hence starting this thread.

Here's another data point. The seller actually used Brasso to clean it. Brasso is a metal polish that is NOT recommended for silver, but I suppose the seller was not aware of this. I've attached below an image of the set before cleaning with Brasso, and an image of the cup after cleaning. I could not make out any base metals, usually copper or brass, in the cleaned cup. If plated, the plating on this kind of plain silver would likely be very thin, and would be eaten away fairly easily by something as caustic as Brasso. The tarnish on the uncleaned and cleaned set seemed fairly consistent with normal silver tarnish. Add in the fact that the metal polish didn't seem to reveal any base metal, that's why I'm taking a risk here.

But absolutely agree that I would want to get it tested, if I ended up purchasing it. Definitely understand that I would be taking a risk here.