Machine Screw with 6-32 threads x 2" long and unslotted hex washer head.

Common piece of hardware used fasten down various playfield parts on almost all Williams/Bally games.

Williams/Bally reference #4006-01113-32.

Fastener part numbering system explained:

The last 2 digits (XX) of the 4 digit fastener part number prefix(40XX-12345-12) indicates the standard stud size of the bolt or screw. For example, part #4006-01030-12 indicates a #6 stud diameter (.138") fastener.

The 2 digit part number suffix for bolts and screws (-12, -04, -16, etc) indicates the number of 1/16" length increments of the fastener. For example, part #4004-01003-04 indicates a screw that is 4/16" long or 1/4" long.

The middle 5 digits describe the fastener head style or other features.

Basic diameters and threads of Standard SAE (Society of American Engineers) numeric system small machine screws are shown below.

The diameters of machine screws are indicated with the number of threads per inch. Here is a list of common sizes in inches:

2-56: 0.0860" or 43/500" in diameter; 56 threads per inch 
4-40: 0.1120" or 14/125" in diameter; 40 threads per inch 
5-40: 0.1250" or 1/8" in diameter; 40 threads per inch 
6-32: 0.1380" or 69/500" in diameter; 32 threads per inch 
8-32: 0.1640" or 41/250" in diameter; 32 threads per inch 
10-32: 0.1900" or 19/100" in diameter; 32 threads per inch 
10-24: 0.1900" or 19/100" in diameter; 24 threads per inch 
12-24: 0.2160" or 27/125" in diameter; 24 threads per inch