could be intermediate within that size range also. Go to Home Depot an try one of that size lamp. Might work.
Here is why I think this based upon the specs:
E12/15 = Candelabra Screw ?" (0.47") Dia. 0.65" Long Base (LCL is at Bot of Base contact.)
E14 = European Screw 0.540" Dia. 0.85" Long Base. Sym. to E-12, but larger & Longer.
E17/20 = Intermediate Screw 5/8" (0.642") (17mm) Dia. 0.82" Long Base (LCL is at Bot of Base contact.)