Could have been Erma, Rohm, RG, Sauer or any of a half dozen others.
25-60 USD or so
erma made alot of guns, alot under military contract to make other guns like lugers and p 38's. any differences from the luger will only be aesthetic
This model was manufactured from 1973 to 1978 by Erma Werke in West Germany for Ithaca.
You specifically have the Iver Johnson TP-25 pistol. These were produced on US-made frames from the Iver Johnson location in Jacksonville, AR with internal parts produced by Erma-Werke in Germany. Your gun was produced in the late 1980's.
50 dollars
Best left to a gunsmith.
You did not say which model. The Erma-Werke KGP68, which looks like the traditional "Luger" pistol, is about $250-$500, depending on condition. If you have a different model, please repost with that information.
10-100 USD or so
The Targetmaster Slide Action, made by Erma in 1985, books at $175 in 100% condition.
Not much. This kind of small cheap imported single-action .25 caliber automatic is often called a "Saturday Night Special." I'd guess the value is about $75 if it works and is in fair to good condition.
What is the value of an ERMA Werke kgp 68 9mm ?