Is there any way to take a single bulb out of The Big Zip-lock Bag Of Xmas Mini-bulbs[sup]TM[/sup] and know if it’s 2.5 volts or 3.5 volts? The guy at Lowes says “No.” :rolleyes:
I have a multi-meter. And a second-hand apron.
What do you need them to be?
I’d say just use them. If you need them to be 3.5 and they’re 2.5, they’ll burn out sooner. If it’s the other way around, they’ll run a bit dimmer.
Thanks for chiming in, Joey P. The 3.5v bulbs are for a multi-function chaser strand and 2.5v bulbs don’t light up fast enough and bright enough to work. I’ve ordered some off eBay, but they’re getting tougher to find each year. The chaser strand may have to go in a year or two. 
Merry Xmas!
Are they really worth the trouble? LED light strings in all sorts of colours and configurations are as cheap as chips these days and use negligible amounts of electricity.
That’s actually an excellent idea, bob++, thanks. Time to leap into the 21st century.
I’m using “cheap as chips” the first chance I get and let my fellow Yanks figure it out for themselves. 
Would this work? Tape up two batteries such that you can make 3v. Get one 2.5v and 3.5v bulb and hook them up to the batteries one at a time. Observe how bright each bulb looks . Then hook up the unknown bulb to the batteries and compare it’s brightness to the known bulbs. I’m assuming that the brightness of the unknown bulb will match either the 2.5v or 3.5v bulb, and then you’ll know which one it is.
Can you measure the voltage drop across a bulb?
Did you nearly get in in Swindon?