The surface treatment of the instrument is the final finish of it. The bass guitar can be varnished or treated with oil and wax.
The varnished instrument could have high gloss or satin matt finish. Neutral color means that the wood is clean, not dyed in any way. Dyed treatment means that the wood is first dyed and then varnished or oiled.
The AV Basses necks on the traditional AVBJ and AVBP bass guitars have always satin matt finish.
The modern models AVB1 and AVBS can also have high gloss finish.
For sound as similar as possible to traditional instruments it is possible to use nitrocellulose varnish, which however has lower protective qualities and durability.
The modern instruments AVB1 and AVBS are always finished with durable hard acid curing lacquer.
If you want to avoid irreversible damage of the finish, only use cleaning agents designated for cleaning bass guitar or musical instrument surfaces for cleaning and maintenance.