One to indicate whether the dollar amount is inflation adjusted or not. I Imagine a $ with an arrow hat on the | So it’s an up arrow and an S. That will work for talking about historical figures in current day.
There is another problem though that is wanting to work backward, either by date or rate. So I would suggest the arrowed $, number and a divisor $14.7m/3.5 this would indicate to divide 14.7 by 3.5 to get the original dollar amount. Even if reading historical documents about inflated dollars, the original amount can be calculated.