String or Hammer ?

[Ron Lindquist]

Have a older L & H  council  that the client thought 2  notes were out of 
tune after I tuned it.   Stopped back today  and the strings 
sounded  (tubby)---    wondering  if  there is a objective way to determine 
if it is the string or hammer.  Pitch was on.   Strings were 
corroded  (copper windings)   and solid were pitted and rusty.

Any insight will be helpful.
Thanks,