They are based on the real life financial institution Goldman Sachs. They are sometimes mentioned on Weazel News in financial reports. The company is owned by the Bank of Liberty as their ATMs have Bank of Liberty interfaces.
They are very well known for their successes and their employees' high bonuses, referencing the lucrative bonuses usually given to bankers at the end of the financial year. This is supported by the fact when Playboy X tells Niko Bellic during Blow Your Cover "I pay like a Schlongberg Sachs bonus!". The Pegorino Family apperently owes money to the corporation as there is the place of start of the Out of Commission chase with Pegorino's men when they may be paying or getting money out of there.
- The firm's name is a pun for the real-world firm Goldman Sachs. Both "schlong" and "schmuck" are Yiddish (i.e. Jewish) terms refering to male genitals. The latter term also refers to jewelry (an analogous euphemism also known in English via the phrase "family jewels"), which frequently includes the use of gold. "Berg" means mountain, so here, "Schlongberg" effectively means a mountain of [gold] jewelry.
- Total Bankers, a subsidiary company of Schlongberg Sachs.