This is a plug in card of the IBM System 360 range of computers.
In order to show more of its construction, parts have been removed.
At the bottom one of two plastic shrouds has been removed,
to reveal 12 connectors, there are 12 on the other side,
and another 24 within the half enshrouded, making a total of 48.
Not all were used, in this example 33 were used.
Mounted on the board itself were 18 square 'cans' and 19 other components.
Seven of the square cans have their lids removed, more about them later.