Amiga Internal Memory Expansion Plus Time/Calendar (1987)
https://www.megalextoria.com/wordpress/index.php/2015/09/18/amiga-internal-memory-expansion-plus-timecalendar/
This ad for an Amiga 1000 memory upgrade is from the July 1987 issue of The Amiga Sentry.
Having never owned the earliest Amiga model, I'm not all that familiar with how these upgrades worked. As I recall, the Amiga 1000 originally came with 256k of RAM that could be upgraded on the motherboard to 512K. If you wanted to go beyond that, you had to pursue other routes. The Amiga 1000 did have an external expansion slot that could be used for various functions. However, you could expand your memory further without occupying that slot via other methods.
Based on the picture, it looks like this particular upgrade board plugged into the CPU socket and then you would plug your CPU into it. This upgrade appears to be plug and play so it was relatively simple to do though not cheap at the time. You could add up to 1.5 GB of additional RAM via this route but it would cost you $599. Adjusted for inflation that would be nearly $1,400 today. But as a bonus you got a real-time clock/calendar with battery backup...