It is a #184. Aside from the horizontal line under the right bottom ribbon that is the most common known design ID characteristic, another just as important is the width of the shaded area around the right side of the vignette oval - it is MUCH thinner on #207. It is the SAME thickness on #184 as on the earlier 3c values. So the two critical ID elements are 1. Soft porous paper and 2. The design element differences. All of these stamps can be identified more easily if you study reference works. My website has a tutorial on the Banknote Issues at
www.stampexpertizing.com and click onto the "Articles" feature.