Mac Pro space saver in Allston! The post title says “Mac Pro” but an intrepid commenter identified the back as a Power Mac G5. In the photo gallery, there’s a close-up in which you can see the video card has one DVI and one ADC video ports; the presence of ADC means it’s a 2003 or 2004 model, 2005-6 models were DVI only.
In some city neighborhoods with substantial snowfall, there’s a tradition of leaving something, a “space saver,” in a street parking space you’ve spent substantial time shoveling out. Cities typically don’t allow them but most people honor them, if not in the interest of community harmony, out of a self-interested desire to avoid automotive revenge by a deranged neighbor. Space savers are typically an old, lightweight chair, a crate, something easy to see but of little value. A 40+ lb. computer is an unusual choice.