Both trimmers look to be from the early 1990s timeframe.
The Homelite looks like a model ST-175. Typical Homelite 25cc half crank engine from that time period, no clutch. These were homeowner level trimmers, but had decent power and reliability. I own a ST-275 (same engine but with straight shaft) that I used for quite a few years. I probably should pull mine out of storage for a nostalgic run, but I haven't used it for several years after getting some used Echo trimmers. The main thing I remember is the Echo units have far less vibration during use than the Homelite. One thing that was a popular alternate usage of these engines was for Radio Controlled airplanes, boats, etc.
I don't have many specifics on the Green Machine, but I recall these being marketed as a more commercial level machine. I notice the Green Machine has HMC on the engine sticker. I believe Green Machines was acquired by Homelite in 1994, so this trimmer would be a pre-1994 model.