PL/SQL :: How To Add Asterisks To Row When One Item In Row Is Duplicated / Show One Row

I totally realize that but here is what im trying to accomplish. I have a table with one column that repeats.the table looks like this.

create table testCheck (check_num varchar2(20), amount number(17,2), invh_Code varchar2(20))
 and it has data like so
INSERT INTO "TESTCHECK" (CHECK_NUM, AMOUNT, INVH_CODE) VALUES ('001', '50', '1123')
INSERT INTO "TESTCHECK" (CHECK_NUM, AMOUNT, INVH_CODE) VALUES ('001', '50', '1123')
INSERT INTO "TESTCHECK" (CHECK_NUM, AMOUNT, INVH_CODE) VALUES ('002', '100', '1234'

 I would like to write a query that would give me the distinct check_num's  but put an asterisk on the items that are actually duplicated.so in other words expected result in this case would look like this. 

"CHECK_NUM" "AMOUNT" "INVH_CODE"
"001*" 50 "1123"
"002" 100 "1234"  

I've been able to get as far as getting the unique values  but what i cant do is figure out for the life of me how to put the asterisk in there.here is my query. 

with Checkquery as (        
SELECT  count(*) over (partition by CHECK_NUM order by CHECK_NUM ROWS UNBOUNDED PRECEDING ) thiscount, CHECK_NUM,  AMOUNT,  INVH_CODE
FROM  TESTCHECK
group by
check_num,
AMOUNT,
INVH_CODE)
select check_num, amount,invh_Code from Checkquery where thiscount ='1';

I simply want to identify the dups put an asterisk on the record and then only select one of the records.