G'day,
I went in search of a Vernier Caliper.
see this link for some terminology:
http://en.wikipedia.org/wiki/CaliperI was astonished to find them at prices from $2 to $90: plastic; cheap alloy; stainless steel - all manner of materials were available.
I bought two, for $2 each: plastic, and the other is chrome-plated.
I got the same answer every time I used them; so I may as well have saved my money.
I'd recommend the plastic: lighter to carry; nothing to rust.
With scales: go for something that uses batteries that are readily, and inexpensively replaced.
While you're out shopping, pick up a magnet: small and cheap is good. Great for detecting some forgeries.
Peter in Oz