Another Ebay Gamble Pays Off... Nice Future Delivery Strip

Spotted this on ebay last week, listed as "U.S: USED #RC20a STRIP/4 CV $240+ UNLISTED AS STRIP".

I'm not sure why RC20a isn't listed as a strip of 4 when RC20 is listed as a strip. I hope to fix that when I submit my changes for the 2019 U.S. Specialized this summer. It doesn't make sense to have one without the other.

Current catalog value as 4 singles for RC20a is $280 (4 x $70) so the starting price of $175 wasn't exactly a bargain... but after some scrutiny I decided to place a snipe. I was the only bidder.

This was the only image in the listing, and at this resolution. What did I see that made me try to purchase it?












Adding some spoiler space...










There was just enough aberration in the strokes, stems, and serifs of the bottom stamp compared to the others, to make me think this might be a strip with the double transfer, which only ever occurs in the bottom stamp of the strip.

And so it is. It makes a perfect matching companion for the RC20 strip with DT I have. Both strips are shown below (new RC20a at left and RC20 at right), followed by a high resolution closeup of the DT stamp.

So, you already had in your collection one with the double transfer ...
How on Earth did you spot it on that low-resolution picture?
... just recalling a remark of my better half: 'stamp collectors are not humans' ...

If I have questions about something contained in an ebay image, I save it into Adobe Photoshop, correct the orientation, and upsample (no more than 100%) and then zoom in/out. You cannot CREATE resolution, but sometimes you can improve it ever so slightly, enough to make some comparative evaluations and see that on the DT diagnostic points (the largest being the FIVE HUNDRED DOLLARS and other lettering in top scroll area) there was just enough difference compared to the other stamps... the lettering looked just slightly more bold than the other stamps.

Here is the original image rotated and upsampled from 72dpi to 144dpi. Yes it makes it blurrier, but look at the comparative size of the white lettering at the top of both stamps. Notice how on the bottom stamp the white areas look narrower or almost "filled in"? That is what I would expect a DT to look like, the offsetting elements decreasing the white areas...

The FIVE HUNDRED DOLLARS and the $5 of $500 are the two places it is most noticeable.

I saw it and saw the DT right away, I just wasn't willing to spend that much on it given that I have two singles already.

So it seems likely that the double transfer occurred at the time that the original plate was laid down. The orange serials were the first and only go as high as 1000. They then switched to the red serials. A great acquisition that helps us answer some question about the production of the $500 stamps.

I have never understood why this did not happen to any of thew other values. Presumably they were all created at the same time on the same equipment and by the same people. It occurs on all of the $500 types but on none of the others.

I suspect that when the plate was made there was a problem in that position. It was then burnished out, albeit incompletely. It was then reentered and what we see as a double transfer is the remnants of the original entry.

Actually this is a prime example of a "twisted transfer" type of DT. The upper left corner shows the twist going up, and the lower left corner shows the twist going further to the left. This would have happened when the position was originally entered, so the entire position would have had to be burnished and re-entered. They probably felt that was too time consuming, assuming that they noticed it at all.

Does anyone know anything about quality control from 1840s until the 1940s, please?
None of the authors I read has anything remote to describing such a process.