Oh, I get it. But a baseline HP Proliant from that era is just an x86 system barely different from a desktop today but worse/slower/more power hungry in every respect.
For history and "how things changed", go for something like a Sun Fire system from the mid 2000's (280R or V240 are relatively easy and cheap to get and are actually different) or a Proliant from the mid to late 90's (I have a functioning Compaq Proliant 7000 which is HUGE and a puzzlebox inside).
x86 computers haven't changed much at all in the past 20 years and you need to go into the rarer models (like blade systems) to see an actual deviation from the basic PC alike form factor we've been using for the past 20 years and unique approaches to storage and performance.
For self hosting, just use something more recent that falls within your priceclass (usually 5-6 years old becomes highly affordable). Even a Pi is going to trounce a system that old and actually has a different form factor.