1. The outer left frame line is broken at the top just as it meets the frame line across the top.
2. There is a short line just above the lower outer frameline that makes the outer frame line appear a bit thicker.
3. The base of the bust should be laying on the inner frame line.

Detail for points 1 & 2 above

These are refered to as "marcas secretas" (secret marks) in the Tort guides.

Of course these cannot be 100% foolproof. Sperati's forgeries also included these marks. In this case you must check the stamp out by it's plating position. Sperati made his forgeries using a stamp from position #10.

1. There is no line inside the lower outer frameline as is discusssed in point #2 for the genuine stamp.
2. There is a large gap between the base of the bust and the inner frame line, at the bottom. The bust should be laying on it, as is noted in point #3 for the genuine.

**NOTE** Unless you are familiar with Spanish stamps, their cancels, and especially issues from this set, you should be very wary of the high values with red cancels. These should be expertized. A genuine red spider cancel on this stamp raises the value considerably, BEWARE.