VIN=Vehicle Identification Number, so just use VIN, not VIN number.
Same idea with PIN.
ATM machine? ATM says it all.
HIV virus? The V tells us it’s a virus.
No need to say something is blue in color, square in shape, absolutely complete, a total disaster or a true fact.
Unless it’s by John Phillip Sousa, no need to say the month of March.
Nine a.m. in the morning? Choose a.m. or morning, not both.
This is my final conclusion.