This is a 1909 plate with a makers seal with number G 7.
This is the one of only a few plates known with seals with letter-number combinations.
Most seals only have numbers.

 

Another 1909 plate with an alphanumeric seal number - L 203
Jarod Nappi
 

This is a 1910 plate with a makers seal number matching the plate number.
Either this is a very big coincidence, or by design.
We don't know which.
Ed Natale
 

This is a 1911 plate with seal number ☆ 1 ☆
Jarrod Nappi
 

Partway through 1913, the dies changed slightly. Notice the pointed "1" on the first plate (like previous years)
and the squared-off "1" on the remake and the later issues.

Here is a 1914 plate with a seal that was stamped upside down !
Jarod Nappi
 

There were several different size and spacing variations in the 1915 plates.

The plates from 10000 to 19999 were shorter than the standard 5-digit plates.
Even if the numeral "1" was in the final 4 digits, the plate size did not change, but the spacing of digits was different.

Here is another example of a plate with an alphanumeric seal number.
This is a 1915 plate with seal number A 20.
Jarod Nappi
 

By the 70000 series, the numeral "1" took up the same amount of space as the other digits.