LF: N28 ferrite material useable on MF ?

[wolf_dl4yhf <dl4yhf@freenet.de>]

Greetings all,
Does anyone have old databooks of Siemens (now Epcos) ferrite materials 
at hand ?
I'm looking for information of N28 material, after discovering a bunch 
of pot cores in the junkbox.
25 mm diameter, 16 mm height, and an AL value of approx. 1 uH per turn 
squared.
The label carries the 'Siemens and Halske' logo, so these cores must be 
quite old.
The plan is to use one of them as transformer to feed the gate of a 
MOSFET which requires floating ground (source not connected to GND, but 
to the drain of another MOSFET).
Is this old N28 material usable at a few hundred kHz, and what about the 
max flux in the core / max density / saturation ?
Best regards,
  Wolf  DL4YHF .