Shekalim 6 a, b

Today we learn about what to do with excess.  We are commanded that the rich give no more than one shekel, and thus excess contributions can go to the voluntary communal offerings.  Or, some rabbis argue, they are chullin, and are not consecrated at all.

Some of the coins and their values are alluded to:
Biblical half-shekel = six garmesin*

darkon (basic currency during the Persian Empire) = two selaim
sela (basic currency after the collapse of the Persian Empire = two shekels = four dinars
teva (next basic currency) = half a sela = one shekel
dinar = half of a teva = one quarter of a sela
tabaah = two dinars

Joseph was sold by his brothers for twenty silver dinars, which is five selaim
The cost of pidyon haben for the first born of Kohanim is five selaim
Because the sin of the golden calf happened at the sixth hour, some rabbis suggest that we give six garmesin as our Shekalim

For most offerings, extra money that was designated to a particular collection cannot be transferred to another particular collection.   It must be donated to the voluntary communal offerings.  Some exceptions include surplus money set aside for olah is used for olah; similarly, extra minchah funds go to the minchah fund and extra shelamim offerings go to the shelamim fund.  Shelamim as animal offerings that have not been slaughtered at the proper time.  Surplus pesach offerings are allowed to go toward shekalim, and surplus collections for poor nezirim are used for sacrifices for other poor nezirim.

In amud (b) the rabbis extend their discussion to the Pesach offering.  I would not have believed that the rabbis had more to say about the korban after learning Masechet Pesachim.  However, I should have known better.  They discuss which animals are allowed to be used as the pesach offering.  An olah is excluded, for it could come from the flock or from cattle, and only those animals 'from the flock' are permitted.  The asham is also prohibited, as it comes from a flock of sheep, but it cannot come from goats, which are also 'of the flock'.  Further, the korban must not be a female animal, nor can it be over one year old.

At the end of the daf, the rabbis question what would be the halacha regarding a person who begins the shechitah with one intention and ends with another.  Could the rabbis imagine that a person would change their intentions in a split-second?  or is there a longer process of shechitah that I don't fully grasp?

Again it is clear that our Sages are defining and redefining categories.  Our halachot are like boxes that hold all parts of human existence.  There is almost always a right answer, a better thing to do.  And we are certainly learning to strive toward that type of definition and structure.  However, at the same time. our Sages offer us their unsolved debates as well.  We learn in today's daf that the rabbis leave the question of piggul status unresolved with regard to an offering that may have become invalid in itself as its human companion changes his/her intention.  The rabbis did not have to include their unresolved discussions.  If these great minds are unable to find a solution in their boxes, they must be teaching us that there will be times where we must live between boxes.