About 30 years ago the following item was in a collection of mine of El Salvador. It, to the best of my knowledge, is unique. It is a block of 50 of the Transito Territorial issue showing the full setting of the overprint. I also had a block of 45 - the top row was missing. I suspect it had been removed because position 2 of the setting shows the third “r” in Territorial being italic (r). This is the only position in the setting with this variety.
There are other varieties as noted in the write-up on this page.
A comparison of the block of 45 with the block of 50 showed these varieties to be consistent and that the block of 50 illustrated the complete setting. It appears that the size of the setting was the largest that could be done by the press in use in El Salvador.
Covers bearing this issue are very scarce although a few are known to exist.
The Color Overprints
In addition to the black overprint, catalogs record the overprint in Violet, Red, Magenta and Yellow. With very, very few exceptions ALL of the color overprints I have seen did not plate into the setting so they must be counterfeits. Nor have I ever seen a convincing genuine postal cancellation on a copy and I do not know of any genuine covers bearing a colored overprint.
Thus, I suspect that at best, the color overprints are either trials to see what color best showed up on the stamp or they were produced for politically connected people as a special souvenir. Caveat Emptor!