Is the worry with the fill nipple that there are rust spots?
These probably don't need to be a concern
When the bottle is realy empty then the fill nipple can move and rattle, when under pressure fit will be sealed.
If you're not confident about the full nipple then it can be easily & cheaply replaced - buy one, or find a friendly player with a well stocked tool & spares kit, fully drain the air, unscrew the fill nipple, make sure no residue drops into the bottle, check the threads are clean (again if necessary make sure any flecks of loctite or bits of ptfe tape are pulled out and don't drop in, check the threads of the new one - if pre treated with dry loctite then use it as is, if not wrap a little ptfe tape on the thread, screw it in by hand and tighten with a spanner. Keep a spanner handy when you go to fill it in case it needs tightening a little
Test date - have a look around for the other markings. There will be a born and a final date which are 15 years apart. See if it makes sense, EG as you were told the next test is next year 2015, then if the test was done at the due time then the final would be 2020, the born date 2005 and the previous test 2010
Failing that to be sure ring hpac and they will confirm the previous test