All parts are listed and described to the best of my knowledge, capabilities and experience.

That a part has been marked as TESTED WORKING, means that the given part has been tested and found to be in working condition. The testing was either done prior to dismounting from the unit or later. If a date is stated it will be the date of testing. The date is usually stated in the form of month/year (i.e. 4/88 means april 1988).
Particularly if many years have passed since testing, it should be accepted by the new owner, that certain things would need doing to the part before using it again;
– Electrolytic capacitors can have dried out to a level where replacement is recommended. Because of their nature, containing fluids that slowly evaporate and dry out with age, it’s generally adviceable to replace electrolytic capacitors in
all things electronic every 20-25 years. Degrading to electrolytic capacitors happens regardless of use.
– Exposed contacts and open variable resistors (potentiometers and trimmers) can have oxidated. Despite perfect storage conditions, airs moisture will always attack bare metal and other conductive surfaces so exposed contacts, potentiometers, switches, relais’, pushbuttons etc. could be in need of a little exercise, a shot of contact cleaning agent or, in the case of certain types of trimmers, replacement before the part can be expected to work again.
– Mechanical things can have seized to some extent. Lubricants dry out with age, leaving potentiometer shafts, gears, motors, switch button rows and other mechanical things in need of an eventual cleaning and a fresh drop of oil.
– Wooden parts can dry out. Many woodsorts contain oil from nature. Woodsorts like teak and palisander (rosewood) will dry out with age and lose its shine when not treated with a light coat of fresh oil every five-ten years. Rub it with a little oil and it’ll be fine again. It’s a general handrule to never treat oak finishes with oil, use wax if you absolutely must do something but be careful, oak cannot easily be restored.
– Dust. All parts were stored for some time, days, weeks, months, years, decades. All parts were stored under the best possible conditions and no dust can get to the parts while storing. Most used parts are fairly clean, still there could be a little dust on a given part but that will be the “original” dust from when the part was dismounted and it will have not have damaged the part or influenced functionality.

So, that a part has been marked as TESTED WORKING doesn’t always mean that you can just fit it and your’e done.
It means that the given part is theoretically, basically and structurally working and it doesn’t have any faults other than what could have set in during storing as described above.

If a part has been marked as UNTESTED, it means just that.
It’s not some kind of “tricky” description of a defective part, it actually means that the part has NOT been tested for functionality. The given part could be defective but it could also be in fine working condition. I can’t tell.

Condition:

Mint = Like new. no marks of use or age.
Appearance is as it would be if just out of its original packing.

EX = Excellent. A used part that only bears the marks from very light use.
Cabinet parts have only microscopic marks – if any.
Electronic parts and circuit boards have no signs of bad or damaged components and no burn marks.
Previous repairs are few or none. Any previous repairs will be absolutely acceptable and decent jobs.

VG = Very Good. A used part that bears little marks from normal use.
Cabinet parts show little marks from normal use/storage. Not particularly obtrusive, typically visible only at close distance.
Electronic parts and circuit boards show signs of previous repairs but none are particularly bad jobs.

P = Present. A used part that bears heavy marks from use, wear, abuse and/or storing under less than adequate conditions.
Cabinet parts will show deep scratches, dents and/or chips, moisture effects and/or missing fragments.
Electronic parts and circuit boards will show obvious burn marks, oxidation, missing components, broken copper traces and/or other faults.
Parts in this category will only be listed if they are considered very rare and/or difficult to find.
Only of interest, really, for harvesting components or for completely rebuilding in
cases where the alternative would be no part at all.

Electronic modules and circuit boards will, unless otherwise stated, have short stumps of the previously connected
leads still on solder tags etc. to ease identification of lead colors when refitting.
Often – but not always – screws, nuts, clips and other hardware used to fit a given part will be included.