Tailors knife? Knife ID question.

[nsantella 17]

I am trying to ID this type of knife based on a sketch.  I was told that it represents an antique knife used by tailors, but that could very well be completely wrong.  The blade is hinged so that it opens when the loop shaped thing on the end is pulled. Didnt come up with anything using basic keywords or image searching.  Without the description I would have guessed it it was a cheap keychain knife, but I cant find one of those that looks like this either. 

If anyone can help with what this is properly called, or point me at a good picture of one that would be great.  Im trying to find one for sale, or enough information to try reproducing it. Thanks!