Here is a quick outline of some interesting points we discussed re: denominations with regard to
Kessef M'dina vs. Kessef Tzori
KM vs. KTz
1. Value of coins covers:
A. Even Ho'ezer re: K'tubbah
B. Yoreh Dei'ah re: Pidyon habbein
C. Tangentially; Orach Chaim re: Machatzit Hashekel
2. Q: What is status of Machatzit Hashekel?
A: No D'oraito because we use half of KM as opposed to KTz
B. Not even a D'rabbanan because no B'rachah...
C. Ergo a Zecher l'mikdash b'alma
D. Contrast this to S'firat ha'Omer - which is also a Zecher per most Poskim - yet also has a B'rochoh. So it seems to be at least a full-fledged D'rabbanan or even a D'oraito according to some.
3. What kind of Kessef is a K'tbbah for a B'tulah?
A. Rabbenu Tam: 100% D'oraito ergo KTz
B. Rif, Rambam, M'Chabbeir and others: 100% D'rabbanan ergo KM
C. Rosh, Mordechai, and current Minhag Ashk'naz: while the Rabbanan created the k'tubbah, nevertheless they insisted on d'oraito money - KTz. Perhaps this is due to "assu hizzuk l'divreihem". Ergo it is a hybrid.
D. Sheetat Agudah / Maharil as quoted by Rema - needs more elaboration.
4. Pidyon Habbein -
A. Still Mid'oraito
B. Ergo requires KTz