Joe,
The scale (eg. 1/87) simply means that the percentage of reduction from the full size item is 87 times. If the model is 1inch long, then the full sized item would be 87 inches long or 87 times larger than the model. Or rather, the model you have is 87 times smaller than the original.
We work here (in Oz) in the metric system (soooooo much easier than Imperial measurement) and it's really easy to figure out a scale difference between the model and the original -
If a full sized item is 900mm long, a 1/87 scale model would be 10.3mm long - that's just taking 900 and dividing by 87.
It's really very simple - even I can figure it out................
Cheers, mate
LeeTree