Dull Gum Versus No Gum Prominent Americans Series

I am in the process or re-cataloging and verifying my mint US collection and have stumbled into a couple regular issue samples that appear to have no gum to me, so should not be included in a "mint" collection to be picky.

One is a 1288B 15c Holmes issue for which the Scott Specialized makes no specific mention of a dull gum issue like others of the series.

The other is a 1304C 5c coil issue. Again the Scott Specialized makes no mention of a dull gum variety although it does for the original 1304 issue.

Could anyone kindly suggest if I have stumbled into rare dull gum (or invisible gum) varieties, or just unfortunately have collected "unused" no gum samples. If the latter is the case (which I suspect), I can just toss them and try to replace with real MNH quality stamps.

Seems like I spend more time and effort identifying low-value issues like these than anything else .

Both 1288B & 1304C were issued with dull gum. Scott doesn't bother with the gum type unless more than one type was used.
Added: Take a close look at the gum with a good magnifying glass, holding the stamp at an angle to the light source. You should be able to see the gum striations, probably diagonal, as long as the stamp hasn't been used.
Hmmm ... think my memory is definitely deserting me. I'm really not sure if you can easily see the dull gum on the Prominent Americans. The gum striations I was referring to are definitely on the Great Americans series.

Without grabbing one of the stamps, the tip to hold the stamp at an angle to a light source is a good one, a dull (dry) gummed stamp will look different than a ungummed one. I've seen more than one listing by a seller who didn't know better saying a stamp was ungummed when I bet it just had dull gum.

Thank you for the pointers!

So are you saying that my two particular examples were only issued with dull gum? If so, that certainly changes the odds of what I'm looking at. If Scott doesn't care enough to mention gum types used, what is a good reference for that information?

The close magnification inspection approach does not yield much for my two either. There are no gum striations. Using a vivid imagination to look for slight color variations (yellowing) of the paper is also not revealing as the paper used on these two issues is also yellowish (or blue in case of the 1283B).

Since I fortunately have a separate collection of used stamps, I was able to pull the identical issues out for side-by-side comparison purposes. The only visible difference was a very slight texture variation to the paper on the backside. The "mint" stamps appear slightly smoother than the "used" samples, with the paper's fibers being a bit more evident in the used stamps. No difference in color is detectable.

If these are examples of "dull gum", I would suggest a new category of "invisible gum" to refer to these issues.

I must confess, I'd be tempted to carefully lick one with tip of tongue and see if it was tacky.

Terry

Yes, both 1288B (Holmes booklet) & 1304C (redesigned Washington coil) were issued only with dull (or dry as it is sometime called) gum. eyeonwall is correct in that there are numerous items listed on ebay as not having gum that undoubtedly do have gum ... it just takes extra effort to see the gum. And many sellers may not know about "dull gum".

I don't collect used stamps, so when I checked my stash of 1304C, I didn't have any used copies for comparison. But, with a bit of difficulty, I was able to see some diagonal striations. When I checked my 1288B, I found a full unused pane plus a used single. The gum side of the unused pane was very smooth while the back of the used stamp was a bit rough. I had difficulty trying to see any gum striations on the unused Holmes stamps however. Looking for striations on the dull gum of the Great Americans seems much easier.
I would guess that, if the back of your stamp appears very smooth, it's probably unused with intact gum. If you're still uncertain though & would like to have a guaranteed unused copy of each stamp, just send me an e-mail with your address. I'll send you one or two of each at no cost (my unused postage pile is rather high at the moment).
Added: One source that does include the gum type (even when there's only one type involved) is the Durland Plate Number Catalog. Durland's perf measurements also are a bit more accurate than Scott's. If you're a plate number collector, this catalog is probably a must ... otherwise it's just an occasionally handy complement to the Scott specialized.

Thank you very much JL for the additional info, greatly appreciated.

After additional inspection and imagination, I guess I'm about to go ahead and accept my examples into my "MNH" volumes. I'm just a bit surprised that these earlier 1978/81 issues were so invisibly gummed. I'm thinking these had to be among the earliest issues that the postal service was experimenting with dry gum processes (for regular issues).

Thanks again!
Roger

You raise an interesting question ... what was the first US dull gum issue? I suspect that there may have been some in the late 60s, but I really don't know. The first ones I remember are, like your 1288B & 1304C, from the Prominent Americans series. For the definite dull gum stamps from this series, the issue date appears to be in the late 70s or early 80s. For stamps issued with both types of gum, Scott doesn't show separate issue dates, but it seems that the dull gum always appeared after the shiny gum ... but how soon after is anyone's guess.
Of course, the real eye-raiser among the dull gum set is J95 (7-cent postage due). With shiny gum it catalogs at the minimum 25-cents ... with dull gum the CV is $650.

Dull gum goes at least back as far as the 6c Eisenhower issue - originally issued in 1970 with shiny gum and later with dull gum, but Scott doesn't say exactly when. However, I do have a reference book that says for booklets, the first use of dull gum was in 1971. A few years later they added a slight yellow tint to the gum to make it more visible.