Slow going and a work in progress but here the schematic around the IC that has the face all shaved off so it can't be identified.
D8 is the Diode in question. This IC chip has just barely enough on the face left to tell it is from SEC. same as the other 2 IC chips.

 

Here you go: https://www.ebay.co.uk/itm/164886172810

 

U1 - KA7500B or TL494
U2 - LM324
U3 - KA7500B or TL494
D8 - 1N4148

 

Here you go: https://www.ebay.co.uk/itm/164886172810
View attachment 245073

Thanks!
Ordered 10.

 

U1 - KA7500B or TL494
U2 - LM324
U3 - KA7500B or TL494
D8 - 1N4148

On further review.....

The KA7500B is a Switching PWM Controller,
https://www.mouser.com/datasheet/2/308/1/KA7500B_D-2314474.pdf

So is the KA5325A
https://www.mouser.com/datasheet/2/308/1/KA3525A_D-2314508.pdf

Would it make sense that this simple board has two IC's performing that same functions ?

The 3 IC chips on this board again are.....KA3525A (PWM Controller), KA324 (Quad Op Amp) and an unknown DIP-16 IC chip

 

U1 - KA7500B or TL494
U2 - LM324
U3 - KA7500B or TL494
D8 - 1N4148

On further review.....

The device is a 300watt Modified Sine Wave DC-AC inverter
It has these two chips that I can identify.....

KA3252A - PWM Controller
KA324 - Quad Op-Amp

Given these two chips in the circuit, I'm trying to determine the identity of the 3rd chip
It was suggested that it might be a KA7500B but that is a PWM controller that performs similar functions to KA3525A.
The TL494 is also a PWM controller.

The KA7500B is a Switching PWM Controller,
https://www.mouser.com/datasheet/2/308/1/KA7500B_D-2314474.pdf

So is the KA5325A
https://www.mouser.com/datasheet/2/308/1/KA3525A_D-2314508.pdf

Would it make sense that this simple board has two IC's performing that same PWM functions ?

The 3 IC chips on this board again are.....KA3525A (PWM Controller), KA324 (Quad Op Amp) and an unknown DIP-16 IC chip
What other functions could that 3rd chip provide that the other 2 don't already?

That said, after reviewing the schematic, I see some connections to the unknown IC that are identical to those for a SG3525