Hi Richard,

A more functional implementation of your solution.

lowerB = 99.434; upperB = 105.566;

MapIndexed[If[Between[#1, {lowerB, upperB}], {#2, #1}, Nothing] &, exampleMat, {2}] //
Flatten[#, 1] &

(*
{{{5, 37}, 104.}, {{5, 59}, 100.}, {{5, 181}, 100.}, {{5, 629}, 104.}, {{5, 785}, 100.},
 {{9, 113}, 102.}, {{9, 295}, 102.}, {{9, 419}, 100.}, {{9, 439}, 102.},
 {{12, 99}, 100.}, {{12, 303}, 100.}, {{12, 653}, 100.}, {{12, 707}, 100.},
 {{12, 803}, 100.}}
*)

While browsing through the FunctionRepository I came across PositionedCases which used a Pattern for matching. It does not work with SparseArray, so Normal is required.

ResourceFunction["PositionedCases"][Normal@exampleMat, _?(lowerB < # < upperB &), {2}]

or

ResourceFunction["PositionedCases"][Normal@exampleMat, _?(Between[#1, {lowerB, upperB}] &), {2}]

(*
<|{5, 37} -> 104., {5, 59} -> 100., {5, 181} -> 100., {5, 629} -> 104., 
   {5, 785} -> 100., {9, 113} -> 102., {9, 295} -> 102., {9, 419} -> 100.,
   {9, 439} -> 102., {12, 99} -> 100., {12, 303} -> 100., {12, 653} -> 100., 
   {12, 707} -> 100., {12, 803} -> 100.|>
*)

Thank you Rohit! That is perfect! And you anticipated my next question which was how to locate entries that are within a range.