Checking out the hastag #hnfpb on Mastodon that #HeinzNixdorfMuseumForum suggest you use, I find the wonderful virtual #ICT1301 #mainframe at https://ict1301.virtualcolossus.co.uk/ by @virtualcolossus.
The computer was a fully transistorised 48-bit word machine with core memory and drum backing store: https://en.m.wikipedia.org/wiki/ICT_1301
(Image in the public domain: https://commons.m.wikimedia.org/wiki/File:ICT_1301_Gothenburg_1962.jpg#mw-jump-to-license)

