On a trip to the doctor, Sheldon uses a PC XT to download rocket thrust to weight ratios from NASA.
Year of feature (shown above)
This is an original IBM PC 5150 (not IBM PC XT 5160) – the fullHD screenshot shows a front panel label “IBM Personal Computer” (not “IBM Personal Computer XT”). Funny fact: the fullHD screenshot also shows a little white arrow cursor in the right bottom of the IBM 5151 monitor screen – it was impossible for this text-only black&green model. A keyboard IBM 1390120 without lock lights was made for later XTs and was compatible with the original PC. But a mouse IBM 6450350 was made for PS/2 model and was incompatible for the original PC model.