Gift of unclear magnitude - how to thank?

[Verruca]

I'm pretty sure I'm overthinking this.  Please talk me down. 

I received in the mail a copy of a magazine.  On the address label was my name, with "a gift from (my cousin)" on it.

My problem: I don't know if this is the first issue in a subscription that she purchased me, or just a free copy of a magazine. 

If I thank her for the subscription and she just arranged for them to send me one issue (perhaps, for example, as part of a "introduce your friends to us" offer), it would be a little embarrassing for both of us.  I don't want to imply that one issue of a magazine isn't a good enough present on its own.  I'm actually touched that she remembered me this year - we don't usually give gifts long-distance, and when the family's together for the holidays, it's strictly token gifts among the cousins.

If I thank her for only the one issue of the magazine and it turns out to be a subscription, it's... I don't know, it just seems a little odd.  I can't explain it in a way that doesn't make me sound like an idiot.  I guess I'd hate for her to think that I assumed she "went cheap" for me.

If it helps to know this, we were very close as children but have become more distant as we've gotten older.

Suggested phrasing, or just slapping some common sense into me, would be much appreciated. 

[ZipTheWonder]

"I'm thoroughly enjoying my magazine, and I just want you to know how much I appreciate both your gift and your thoughtfulness.  Thank you!!"

[JudiAU]

Call the publisher. They will be able to tell you have an active paid subscription in your name.

[Maggie]

You should be able to tell by looking at the label.  It should have a date on there although usually in code but it's not impossible to figure out how long it's a subscription for if it is a subscription.

[MineralDiva]

Just call her and say, "Thanks so much for the magazine!  It was sweet of you to think of me!"  Whether it's a one-off, or a subscription, the sentiment remains the same.

[Telmereth]

I would probably go with something like:
"Dear Cousin, thankyou so much for thinking of me! You know how much I enjoy reading about cars/cats/knitting, and this magazine is one I've never tried before!"
I've been in similar situations, and believe me, it pays to be vague!

[Verruca]

Thanks for the suggestions!  The label isn't very clear, and it isn't a big enough deal for me to call the publisher directly (though those are good ideas!)  Normally I prefer to be fairly specific in thank you notes, but in this case I think y'all are right and vague's the way to go.

Woo!  I knew the e-Hellions would come through for me on this!