The item listed here is a Bakelite black hand-held receiver cover or case for an antique wall or candlestick telephone.  This does not have the inside parts!  This piece is about 4-15/16" long and the horn end is 2-3/32" OD.  The horn end has a female threaded opening recessed about 1/2" into the horn, and the diameter of the thread is 1-1/8" ID.  Around the hole for the cord it says "Stromberg-Carlson Phone Company.  

I have another one listed that has a slightly different design and measurements. It does not have a manufacture's name.  It is also a bit light (weight) material.