It's hard to tell how old your Radom is from the description, but you might have something worth taking care of.
Polish Radom pistols of the P-35 type date back to 1936 through WW-II. More recent pistols are known as the VIS P-35 and these were also made with a slotted grip for a shoulder stock (in 1997 only).
You might want to carefully inspect your Radom for other markings that might have been partially filled in during the plating process. Guns with Nazi Germany acceptance markings demand a premium. Original condition Radoms can fetch up to $2500. Even the 1997 VIS P35 can bring in $2600 if still like new.
I suggest using Google to search the net for "Radom" + "P35" and see if you find some enthusiast group or individual who can help you identify your gun. Gun Parts Corp
lists the part as #13 in their exploded diagram and it's called a "Hammer Drop catch" (looks like a Walther P-38 style safety lever to me). List price is only $14.40 but they are currently out of stock.
See: Gun Parts Corp - Radom