My Big Grandpa's Coat of Arms

A year or so ago I posted this online: 

Before you say it, I know this is mail-order fake heraldry. All the same, I found it amongst my late Big Grandpa's effects almost 40 years ago and would appreciate some help blazoning it, and what it may have represented.

I received the following replies:

The "S" stands for "Slapczar..." (can't read the entire name). The eagles, blue shield overall, and paly-looking thing make it more heraldic-looking to people who don't know heraldry.

Even if it was actual heraldry, Eagles got picked a lot because they look cool. Generations later people could retcon all kinds of contradictory things into grandpa's decision to choose an Eagle, but they were almost certainly wrong. Grandpa just thought an Eagle was an important, prestigious, animal that looked cool on a surcoat. Palys are a nice, distinctive pattern that looks nice on a surcoat.

Letters are rare, and basically unknown outside of Iberia. This is partly because heraldry developed in the 1200s-1400s when literacy was minuscule, and partly because heraldry has to be legible on a dude's surcoat 300 ft away.

RE: Letters, interestingly enough, they pop up a few times around Silesia. For example in Zittau, or Wroclaw

Blazon for the shield could be something like:

Quarterly First and Fourth Or, Second and Third Tenné an eagle Azure, in the first a Gothic letter S Sable, in the Fourth a pallet and sides sinister and dexter all Sable, an inescutcheon Azure