The “<NOUN>s’s” construction comes up quite often in signs, at least in my neighbourhood.
I haven’t seen a legal use of the arrangement, though — and I wonder, is it at all possible?
If it is, under which circumstances?
Rule 1: Many common nouns end in the letter s (lens, cactus, bus, etc.). So do a lot of proper nouns (Mr. Jones, Texas, Christmas). There are conflicting policies and theories about how to show possession when writing such nouns. There is no right answer; the best advice is to choose a formula and stay consistent. Some writers and editors add ‘s to every proper noun, be it Hastings’s or Jones’s. And there are a few who add only an apostrophe to all nouns ending in s—however, this method is relatively rare, and not recommended here. One method, common in newspapers and magazines, is to add an apostrophe plus s (-’s) to common nouns ending in s, but only a stand-alone apostrophe to proper nouns ending in s.
Examples: the class’s hours Mr. Jones’ golf clubs The canvas’s size Texas’ weather
Another widely used technique is to write the word as we would speak it. For example, since most people saying, “Mr. Hastings’ pen” would not pronounce an added s, we would write Mr. Hastings’ pen with no added s. But most people would pronounce an added s in “Jones’s,” so we’d write it as we say it: Mr. Jones’s golf clubs. This method explains the punctuation of for goodness’ sake.
Rule 2: To show plural possession of a word ending in an s or s sound, form the plural first; then immediately use the apostrophe.
Examples: the classes’ hours the Joneses’ car guys’ night out two actresses’ roles
The only case where you might see s's with a plural noun is in names. For example, the Moss family's home could be called the Mosses' home, but it might also be called the Mosses's home. My own last name ends with an "S," and my family has a sign that uses the extra "S" following the apostrophe, but I would never have added it myself.
You'll see s's is when the singular form of the noun ends with "S," of course, like in princess's. When you have a plural ending in "S" (most plurals), you add only an apostrophe, like with princesses' or cats'.