Topband: LU5DM or LU5FC or Both?

[Joe Giacobello, K2XX]

Last night, just before heading for bed at around 0400Z, I checked 160M 
and distinctly heard LU5DM calling CQ on 1834 KHz.  I worked him and was 
quite delighted since I had never even heard LU on top band before.  I 
proceeded to make out a QSL and envelopes, and then listened to1834 
again where a pileup had developed.  However, now the LU station was 
signing LU5FC on the same frequency and at about the same strength as LU5DM.

I suspect that there were two operators with different calls using the 
same station.  Before I send my QSL, etc. to LU5DM, can anyone confirm 
that LU5DM was indeed the station originally on that frequency at that time?

Thanks for your help.

73, Joe
K2XX