The IoM is different than for example England+Wales - the Mormon's obtained permission to microfilm everything in the Roll's Office c.1950 onwards and as under Manx Law (ecclesiastical) all wills had to be proved within 1 year and recorded in the court records this meant all wills. They also filmed the majority of the Manorial records.
The IoM is also different wrt property deeds - since 1702 these too have to be registered with the courts and the Manx Museum now has most deeds pre c.1900 - but these are not microfilmed (in fact they are probably the only original records still used by family historians). An index to them giving the place as well as the two main parties would be a great benefit.