stopwatch features on calculators

[Harald]

I keep an RFT MR411 with my photography development kit. Allows me to do the necessary calculations (mixtures for the chemicals, temperature compensation, etc). It is a but cumbersam due to the lack of RPN, but fine for these simple tasks. And it has a stopwatch (with lap and split) that I use to time the development process.
It would be much nicer to have an HP55 for the job, but I don't want to keep it with all the chemicals...