Sounds like you have an Intermatic mechanical timer.
If I were you, I would save a bunch of money and go to Lowes and just buy another pair of mechanical timers. They're only $40 each. Here's the Lowes description: Intermatic 24 Hour Water Heater Timer, 250 Volt, Item #: 26399, Model: WH40-6-250V. I replaced mine last year. I didn't have to replace the box, I used my existing metal box and just used the timer mechanism out of the new timer. Easy!! The digital ones you are considering seem to cost about $150 each. For a timer - Ouch!