MICS-6814 fake? (Multichannel gas sensor)

[MatGO]

Hi, I got "purple board" MICS-6814 sensor from aliexpress. It is also known as CJMCU-6814. I go through datasheet and all topics I found here many times but I was not able to get it working at all. I found schematics of "Grove Multichannel Gas Sensor" and prove the connection with pull up resistors on sensor outputs is correct.
I was getting 5V output with pull-ups all the time, no matter the resistance I set. However I was getting different results when hooked the resistors / potentiometers to the ground.
I evaluated sensor might be wrong or soldered in wrong direction so decided to unsolder it from PCB and check the position mark at the bottom.
What a surprise - there is no position mark at all.

Regarding datasheet there should be mark near by "A" PIN. The sensor I got does not have mark at all. This lead me to think the sensor might be a fake.
What is your opinion? Did you ever see genuine sensor from bottom?

[b707]

@MatGO

Regarding datasheet there should be mark near by "A" PIN.

Regarding the datasheet the mark can be just painted on the surface and after soldering/desoldering can be gone at all...
But I agree it's suspicious

[Koepel]

There are two photos of the bottom online.

At the website of manufacturer here and on a other website here.

The sensor that you have might be fake or from a discarded batch.
Does your sensor have a different color ? In the photos it is grey and the real sensor is not that grey.

Adafruit has a similar sensor: https://www.adafruit.com/product/3199. They only sell things that they test themself. They manufacture the pcb and the modules themself. They have tutorials. They buy the components from reliable and well known distributors.