Original product name: Genuine Intel CPU 0000
Original product name: Genuine Intel CPU 0000
The model refers to a specific processor configuration—ES means Enhanced Speed, QS stands for Qualified Speed Indicator, and QQBY indicates the base quality level. It usually describes the performance and features of this i9 chipset. Regarding the unlocked status, if it's unlocked, it might be possible to adjust the settings back to a standard level, but it depends on the manufacturer’s policies.
A QS and a ES chip are two very different things. QS= Qualification Sample - These are review units typically, they are nearly as good as the consumer grade product. You do run the risk of someone who had this before overclocking it excessively and doing damage however. ES= Engineering Sample - These vary wildly in quality. Early versions can be buggy messes, overclock poorly, and just not work right at all. Later versions can be very close to the retail chip with just lower stock clocks. These are riskier. The chip you are looking at is an Engineering Sample not a Qualification Sample despite the misleading listings online. This thread provides a bit more detail about the particulars of the one you are looking at.
I operate a QS Xeon 1660v3 similar to an i7 5960x that I purchased with a subpar memory controller (only four of eight slots will function). Despite this, I spent $112, which was a significant savings. These chips carry a considerable risk, especially with ES CPUs, but at such a low price they can be worthwhile if you're comfortable with the potential issues. At around $340, they’re hard to recommend. The Ryzen 3700x offers better value with a warranty and no risk. You might also look for discounts on a 7820x that’s been disassembled, which could provide a solid CPU at $250-300. I’ve seen those on Reddit hardwareswap for similar amounts. If you locate a 9900k unlocked ES chip for $250, it might be worth the gamble.