Same thing here, without it right in front of me I can just guess as to if it uses a seal on the exhaust side or not. Typically it really don't need one there, but on some engines they'll put a seal on both valves. Since there's a posative pressure at the valve guide it can't leak while running but some vertical cylinder engines may smoke a little just at startup if oil does seep past the guide after shutdown, but even if it does, the oil loss is very minimal like less than a drop each shutdown. Both statements above are right tho, it just depends on what the engineer decided to do there when he designed the engine.
One thing for sure is there should be something there to prevent the direct contact between the spring and the aluminum, sometimes it's just a thin washer and other times it's machined to fit the spring perfectly and keep it centered over the valve spring land.
Being that these engines are Honda clones it should be no problem getting a replacement part, and at the worst, it may take a call to Harbor Freight so they can order a new spring seat.