Fact: Everyone has problems when grading older lures or boxes because it is totally subjective.

(Subjective: an adjective; of or resulting from the feelings of the person thinking; not objective; a personal feeling or opinion)

VISUAL VALUES:

Visual values vary considerably from person to person. As we all know, not everyone has good taste or appreciation for details. (What other explanation is there for people who buy ugly dogs?)  

TERMS:

• Water marks: caused by, as you suspected, being soaked or wet.  It usually leaves the paper rippled or caused running together of the colors or a line where the dye bled.

• Sun damage: from long-term exposure to sunlight which fades the colors of the labels or box. 

• Oil damage: If a cardboard box was in a tackle box long-term, it is not unusual that it would get oil on it and that would darken the box.  Wood boxes seem to be particularly subject to oil damage as it soaked into the wood.

• Preservatives: it is not uncommon for some well meaning soul to spray or paint varnish on a box to preserve it.  In fact, what they did was ruin it.

• Stiff vs. Mushy cardboard.  If you wet cardboard, it gets mushy and is no longer stiff. 

GRADES:

Mint--Box should look like it came off the shelf. Crisp, no dirt, corners sharp, and no wear. All lettering crisp and clear. Price tags or written price should not detract.  Structure of the box must be stiff and unwarped.   No water marks or sunlight fading damage.  The box shown is about as close to excellent plus as you can get and it is from 1916.

Excellent--Box will have very minor wear to the corners and some wear around the edges. All wording and lettering should be clear. No rips or tears. Price tags or written price should not detract.  Structure of the box must be stiff and unwarped.   No water marks or sunlight damage. The box shown below would be excellent minus due to the corners being slightly worn.

Very Good--Box will have wear to corners and wear around edges. Box may have light soiling or light water marks. Box may have very minor tears (e.g., paper label applied that is starting to peel up) or very small dents. Some of the lettering may be slightly worn.  Structure is still there, box will be square at corners and along panels.  No mushyness to the side or tops.  The Neverfail box below is very good minus and Heddon is very good.  

Good--Box will have dirt, stains or water marks. Probably looks "dingy" overall. Lettering will be worn, but you should be able to read part of it. Box may have tears or repairs with tape.  Structure may be distorted and joints of the box may be split.  Sides of box are not straight or stiff.  The box below is in only (good) condition due to having been wet.

Poor--Barely readable lettering. Stains, soiling, with tears or parts of the box missing (end flap, etc.).  Structure is gone, box not stiff or squared.  Sides, bottom or top may be mushy due to water damage.