The 105.012 is the first asymmetric case Speedmaster, and the first are marked -63 in the back and have a dial without T marks. This reference was produced at a similar time to the 105.003 until it was replaced by the 145.012 in about 1967. The 105.003 continued to be released by the factory until 1969.
Original pushers on this reference are 5mm wide and 3mm tall (Strictly speaking they are 2.7mm tall but very hard to measure in situ.) and are known as Short and Fat pushers, or mushroom pushers. The original ones have fat necks when compared to service replacements.
For me the shorter fatter pushers are very attractive and fit with the case perfectly, and I especially value the originals with the fat necks.
Below is a side by side comparison with the original pushers on the left hand case.