White's have the earlier Coinmaster series with the Coinmaster I, II, III and III Plus. These were in more squarish-shaped housings and powered by 3-9V batteries.
Then they brought out the Classic SL series and those included the Classic I, Classic II and Classic III. The III was similar in controls and features as the Coinmaster III Plus and had the Frequency Shift and Normal/Black Sand toggle. All of those were non-display models.
About 1998 they introduced the Classic ID. This was basically the Classic II with the two knobs for control plus the target ID display. It also had a 'front-end' change from the Classic II that allowed it to use the Blue Max series of search coils.
That was later followed by the Classic IDX which was basically a Classic III SL with the Classic ID's target ID display added. About 2001 they had some model changes and renaming and the Classic IDX was renamed the IDX Pro. Same basic detector but had a matte-finish decal under the display rather than the bright shiny, silvery decal of the Classic IDX.
Monte