Thanks for the input, folks!
The song about a 'maiden fair to see...' is a different song. (It's often said to be the one she sang--it's even included on an album of "Songs from the Little House books," but Laura was singing about deceptive men... ;^)

The "guard" around their neck is something that will make them appear "good" or trustworthy--but I was wondering if anybody knew WHAT?!?

Here are the lyrics--

BEWARE, OH TAKE CARE
(Blind Alfred Reed)

They say young men are bold and free
Beware, Oh take care.
They'll tell you they're friends, but they're false, you see
Beware, Oh take care.

chorus:
Beware, young ladies, they're fooling you,
Trust them not, they're fooling you!
Beware, young ladies, they're fooling you,
Beware, Oh take care.

Around their necks they wear a guard (Beware, oh...)
And in their pocket is a deck of cards. (Beware...)

They smoke, they chew, they wear fine shoes (Beware...)
And in their pocket is a bottle of booze. (Beware...)

They hold their hands up to their hearts
They sigh, Oh they sigh,
They say they love no one but you
They lie, Oh they lie.