Collectibles is an imaginative supplement of TSO, also like it, but...
1. They use wrong stock size in Trade Office when preparing offer. The tooltips and amount slider's endpoint is stucked on the store level of time when collectibles implemented, didn't follow storehouse developments have occurred since then. It is probably a bug, should be in bug section, but there are some more misconceptions on similar context:
2. The christmass event deactivation conjured christmass collectibles out of Mayor's, so now we can check them amounts only in TO... no comment. They should be in Event resources section till next event apperance, or should remain in Collections with inactivated buff production button; because we can trading them, so we have to plan for them. Anyhow, we need to know easily accessible what and how much we have.
3. In Mayor's house could not check the real amount of collectibles over 999, tooltips show only names, no details---in contrast other tabs of Mayor's. We need to know exact numbers, not really indifferent what the 1k means: whether 1,000 or 1,999...
4. The time needed to complete collection don't appear anywhere, nor on confirmation panel (only the needed resources). The duration is reveal just after clicking the OK button, no way back... Beyond that we have to decide without correct information, we are prevented from check details on collection tab during the buff creation, so not indifferent how long it is. (Similar problem in Prov. houses: you get the time only when no way back...)
5. Tinkling notification appears when collection buff is ready, clicking on it opens Mayor's Basic tab instead of Collections; the unnecessary one more click just annoying. Sometimes this way opened Mayor's have to be closed and reopened, because the timer is stucked somewhere in middle, so collection buff could not be picked up; this should be a bug...
...so, I like concept of collectibles, but devs should polish a bit the realization.