Remember that you are very unlikely to listen to a pathologic murmur in the CS exam. The SPs are healthy individuals who are trying to fake an illness. If they seriously want you to listen to a murmur they will make a funny sound with their mouth while your are listening. In that case you need a good ear not a good stethoscope ) just joking.
The evidence that you won't see pathologic murmurs in the CS is that these murmurs are being increasingly tested as audio files in the written Step 1 and CK exam and so there's no need to test you further regarding this issue.
The same applies for respiratory sounds. The SPs will whistle while you listen to tell you that they have a wheeze. Or they roughen their voice while you test for vocal fremitus to tell you this is consolidation but you'll not actually listen to real adventitious sounds. Think about it, how come they keep a wheezing patient in the testing center from 8 AM to 4 PM! They'll never do it.
Having said that, any stethoscope will do. Any standard stethoscope is enough for the CS exam.
By the way if you go to the center without a stethoscope they'll give you one.
I think u need to worry about other things than the brand of ur stetho!!
I used the one I have been using throughout med school..lets see..that makes it about 6 yrs old.
as long as u can hear thru it, u can use it!
I remember I was worried about what kind of white coat to wear..long ? short? turns out, everyone was wearing one of a different length! it does not matter that much what u wear. there were some girls wearing red pants and red shoes!
I wud not recommend such things, but relax, and concentrate on studying!