3 lb Michigan axe head

[axemanalan]

I have a 3lb Michigan pattern axe head. It is vintage but in good shape, my guess is post WW2. On cleaning it I found the letters NP T-60, on both sides. One near the top of the head and on the other side in the middle of the cheek. The letters are quite small but clearly legible. It looks as though it may originally had blue paint on the head. Nice steel, cleaned up beautifully and takes a good edge. No known maker marks like Plumb or True Temper. Does anyone have an idea as to what those markings mean?

 

[Hickory n steel]

We need pictures.