I recently acquired the above. It is in bhr with a Parker Duette style top fitting clip that has two pieces cut out like a dollar pen.
The barrel says it is made in England but the screw in steel nib unit says:
RELIEF (curved over)
ESTERBROOK (curved under)
MADE IN USA
It is a lovely broad, almost italic nib. What I want to know is when did Esterbrook start putting numbers on their nib units? I think it pre dates the Conway Stewart Relief pens, so should be early to mid 1930's but that is purely conjecture.