It is always best to show another instrument hooked up as well and both show the same value.
This increases the confidence level steeply.
Not too many sellers do this on ebay and it is so simple.
As long as you make it abundantly clear that the other instrument is not for sale as part of that listing.
I can't tell you how many times people have bid on my items without even reading the damn description! For example, I can write in large bold, red, underlined, text that an item is for pick-up only and shipping is
not available, yet I'll still get people messaging me asking how much shipping is to their location (after they've bid and the listing has closed).
It's almost at the point where I could say the package is just a house brick, nothing more and someone will still bid on it. Yes, people are dumb!