Bava Metzia 72: Postdated and Antedated Promissory Notes; Publicizing the Price of Produce

The rabbis go into minute detail about the halachot regarding lending and borrowing to people who move from one 'category' to another. For example, if a person converts to Judaism after lending money to a Jew, is he permitted to collect the interest? or just the principal?  The rabbis are concerned that people will speak rudely about these people, saying that they converted or did not convert because of an interest in money.

Is a postdated contract ever valid?  What about antedated promissory note?  What could go wrong if these agreements were enacted?  The rabbis have different opinions about these different notes - in a number of different contexts.  Although they are lenient regarding some situations, the rabbis are careful to consider the potential consequences of permitting notes that are not enacted at the time that they are written.

A new Mishna teaches that one must wait until the market rate is publicized before setting a price with a buyer for produce that will be delivered in the future.  Although the seller might not have the produce in hand, once the market rate has been set, another seller will have that produce, and thus it can be acquired at the stated price.  If he is one of the first to harvest his produce, he may set a price for grapes (for wine), a stack of grain (in his possession already), clumps of clay for building or plaster for the kiln.  Manure may be promised at any time, for it is always available.   He may not set the price exorbitantly high, for if the price changed, the buyer could walk away from the transaction.

The Gemara asks: does this apply both to large and to small markets? does this apply to prices for both new grain and old grain? who can set his/her price at the gleaners' rates?  Different cities might have different availability of produce. How might this affect the arrangements of buyers and sellers?

I am hoping that tomorrow's daf will share more detail on the parameters of publicizing a price.  Was this done exclusively via word of mouth? Were there formal announcement?  If so, when and where and by whom?