Remembering the guys at Mandarake, their 
knowledge of anime (particularly relating to the 
lesser priced ones that you're both referring) 
was pretty limited.  The clerks were from a 
slightly older generation and thus the anime 
titles they personally recognized stemmed mostly 
from stuff around or before the late 90's.  
Honestly, I think they were just making educated 
guesses like you both are.

I also don't know who this character is but you 
might find out by researching the character 
designer for the Saber Marionette series, 
Tsukasa Kotobuki, and find out what other titles 
he has worked on (like Akihabara Dennogumi and 
Battle Arena Toshiden).  And keep in mind there 
are many Saber Marionette series too, and your 
cels might have appeared in one of them.

Here's the bio on Tsukasa Kotobuki from Otakon:

"Some people can spot a cute girl from a mile 
away. Tsukasa Kotobuki makes a living creating 
them on paper. Kotobuki-san got his start as a 
professional back in 1995, as the character 
designer for the fighting game, Battle Arena 
Toshinden on the then-brand-new Sony 
PlayStation. After working on both sequels to 
Toshinden, he made the jump to the animation 
industry, designing the cute female leads 
of “Saber Marionette J.” In addition, Kotobuki-
san created a number of original characters for 
the television show.

With the immense popularity of “Saber Marionette 
J” and its art style, Kotobuki-san was given the 
chance to adapt his own original story to 
television. In 1998, “Akihabara Dennou Gumi” 
(“Cyber Team in Akihabara”) aired. With initial 
character designs and a story by Kotobuki-
san, “Akihabara” only added to his growing 
popularity. Two years after “Akihabara,” he once 
again made another jump from character designer 
to mecha designer with “Ginsou Kikou Audian” 
(“Attack Armor Audian”). With the new 
millennium, Kotobuki-san can be found drawing 
the manga “Ragnarok,” appearing monthly 
in “Shonen Ace”. (Not to be confused with the 
Korean “Ragnarok manga” published domestically 
by Tokyopop.) 

Also, true fans may be able to find his current 
art in small comic shops and online; Kotobuki-
san spends much of his free time creating 
doujinshi, or fan-manga."