Stamp 2136 Bread Wagon Questions

on stamp 2136 bread wagon I have a coil set of 3. It looks too perfect to be an "unused" removed from envelope stamp but there doesn't seem to be any gum on it. I've seen this condition on other stamos too. I took another one that was a single and had what appears to be "no" gum or just so dull it is invisible and I wet my finger and touched it and it stuck like glue. Do some new stamps come with invisible glue? Is there a list of these somewhere?

Also on the bottom of the middle stamp of the trio is a number 4 and on other singles I have i've seen 1 & 3 so I assume there are some with a 2. I thought it Was this to make it easy to count how many are left on a roll or something but the coil of 5 I saw had 1 one on the middle of the strip of 5 but nothing on the other 2.

This stamp has what's called dry or dull gum. There is no shine to it. The number at the bottom of the stamp is a plate number. Numbers 1 to 5 exist. The plate number appears at intervals of either 48 or 52 stamps on the roll depending on which press it was printed on. Plates 1 and 5 have the 52 stamp interval while plates 2, 3, and 4 have the 48 stamp interval. See this page from the Plate Number Coil Collectors Club website.

https://pnc3.org/Data/Breadwagon.php

The Plate Number Coil Collectors Club website has much information on all coils issued since 1981. The home page is at https://pnc3.org/