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8. Die Links, Die Axis, AES Scale

Should coins be found that have been struck on the same obverse or reverse die, they are described as being "die linked". Coins sharing identical obverse and reverse dies are said to be "die duplicates". As described earlier, reverse dies wear out more rapidly than obverse dies, so obverse linked dies are more likely to be found than reverse linked dies.

Die Axis is a term used to describe the alignment between the two dies used to strike a coin. The die axes of thirteen Ostian minted coins are indicated below in Table 10 using the numbers on a clock face for reference (degrees are also used by some authors).

The AES Scale is used to divide all bronze coins from the later issues (including those minted at Ostia) into one of four groups. The criterion used is the diameter of the coin in mm. And where coins are not perfectly round, the greatest diameter is measured.

Key to the last column of table 10: AE1 = 25 mm.+; AE2 = 21-25 mm.; AE3 = 17-21 mm.; AE4 = less than 17 mm.

Table 10: Die axes, reverse images, alignment of laurel wreath, mintmarks and AES types.
No.	Axis	Reverse Image	Upper part of laurel wreath pointing towards these letters in the inscription	Mintmark	AES type
1	12/6	Dioscuri	NT	MOSTP	2
2	12/12	Dioscuri	N	MOSTP	2
3	12/11	Dioscuri	T	MOSTP	1
4	12/12	Dioscuri	N	MOSTS	1
5	12/5	Dioscuri, she-wolf and twins	NT	MOSTA	2
6	12/6	Dioscuri	TI	MOSTS	1
7	12/6	Dioscuri, she-wolf and twins	NT	MOSTB	1
8	12/11	Dioscuri	NT	MOSTQ	2
9	12/11	A Genius	IN	MOSTT	2
10	12/5	Fides	NT	MOSTS	2
11	12/12	Dioscuri	T	MOSTQ	2
12	12/1	Dioscuri, she-wolf and twins	T	MOSTT	1
13	12/6	Fides	NT	MOSTQ	1