Many professional fast bowlers are able to reach speeds of over 85 mph, with a handful of bowlers in the world able to bowl at 95 mph+.
Between 1730 and 1740, 150 cricket matches were recorded in the papers of the time.
Conversely, slowing the scoring rate can put additional pressure on the batsmen and force them into taking extra risks, which will often lead to wickets.
That would give me a starting point to know where potential scamming is taking place.