Here is premium reproduction shell and cap for a telephone receiver.  These shells are  specially made to fit either a magnet type receiver or a U1 type receiver element. If you wish to use a U1 receiver element this is your best solution.

They can be used on candlestick and wood wall telephones 

  They are the best quality reproduction receiver shells currently available on the market. As you see the come polished .

The shells will fit many receiver caps made by Western Electric, Northern Electric, Leich and other manufacturers, including some reproduction caps.