There are many reprints of this small shield series. Some official, other illegal but done by Roberto Lange, the original printer. The main thing to look for is the "C" of centavos. Only the 5 centavos has a small C, if you see a small C on either 10 or 15 centavos, like on the example you show, you immediately know that this is an illegal reprint or forgery.
re: Is this a forgery?
There are many reprints of this small shield series. Some official, other illegal but done by Roberto Lange, the original printer. The main thing to look for is the "C" of centavos. Only the 5 centavos has a small C, if you see a small C on either 10 or 15 centavos, like on the example you show, you immediately know that this is an illegal reprint or forgery.