A set of 4 64K x 1-bit DRAM chips. 150ns access time.
These will either be new old stock, or recovered components – but in either case, they will have been tested in a suitable computer to ensure they are functioning correctly. This is an important difference to many RAM chips sold on eBay and the like, which are not tested – and there can be around a 5% failure rate on these 30 year old components.
Please note that strictly speaking, these RAM chips are said to not be suitable for a Dragon 32 or 64. This is because they require a 256-cycle refresh, but the Dragon’s SAM chip only supports a 128-cycle refresh. In practice, I have not actually seen these chips fail, but ideally, for a Dragon, you want the KM4164 chips instead.