Observations began back in 1992 when myself and the late Swedish Variable Star observer Margareta Westlund worked closely to monitor this star. We were the only observers at that time.  It was originally classified as a Mira star, but rumblings in Latvia suggested otherwise - and we wanted to find out more!  Dr. A. Alksnis of Latvia Academy of Sciences suggested a period of 790d in the mid 1990's, a phenomenon unheard of in RCB stars.  

Classical RCB stars are known to be highly luminous, hydrogen deficient stars. DY Per is only moderately hydrogen deficient, with no spectroscopic evidence for high luminosity. Recently a new subgroup of RCB stars has been suggested - the DYPER sub group. The fades and recovery of DY Per are more symmetrical than classical RCB stars, with the beginning of a decline usually slower, accelerating as the fade progresses. The minima also appears shorter in duration. 

New analysis (2016) from my own data suggests a period of 789.7d, four days shorter than the period measured 10 years ago.