I am backtesting some of John Locke's youtube M3 trades and have discovered that the option price (MktPr) has changed from the time John posted his video until today. I will call OV tomorrow to ask why but I thought I would post a question here to see if anyone else has come across this. I am attaching 2 pics. One pic is a screen grab from JL's 12/15/14 trade. Look at the MktPr for Jan 1050 P. It shows 28.15. The other pic is from backtesting today and it shows a price of 33.30 for the same option. Why the difference? I have stepped thru by 30 minutes, checked on different days around this same time period and I am seeing these large price differences. So then I downloaded ov archive data for 2014 and replaced this data in my archive file. But my price stayed the same 33.30 In the Model for RUT I have all the JL recommended settings including MktPr = (10B +10A + Last)/21. Any ideas on such a big difference? I have been away from using ov for the past couple of years, was there some type of historical data change? If you go into backtrader on 12/15/14, what price do you get for the Jan 1050 P?