A SUPER digital thermometer can be had for $37 - maybe better on eBay. I just got a model DM6801 which includes a 5 foot K-type thermocouple, and it's temperature range is: -50.0 to 1999.0 °F (-50.0 to 1300.0 °C)
Just got mine today, plugged in the wire - and the response is amazing! HUGE easy-to-read LCD digits... This may be overkill - but won't break the bank and can be useful so you don't have to open the oven to check temps on a non-digital stove - and then can use it to check your proof box!
Available from this seller:
http://www.meter-depot.com/digital-1-k-type-thermocouple-thermometer-dm6801/
as well as eBay and around the web. No affiliation with anybody - just a neat product you may want to add to your kit!