Do not put square bracket [[]]. Do not put "|100px" here.
width
recommended
Recommended because it can prevent lengthy text to inadvertently enlarge the box. See examples below for the reason why we need 2 instances of width. Just an integer, not "100px". Highly recommend to use an even number.
alt
recommended
empty
Alt text for readers who can't see the image; see WP:ALT
{{Coin image box 1 double
| header = 500 Japanese yen
| image = Image:500JPY.JPG
| alt = Two sides of a coin. The front contains a plant and the back contains "500" in big digits.
| caption_left = Paulownia, state title, value
| caption_right = Value, bamboo, Mandarin orange, year of minting, latent image
| width = 200
| footer = footer text here
| position = right
| margin = 0
}}
{{lorem ipsum}}