[Radioroslyn]

Unfortunately Philco doesn't give us much to go on. The resistance and inductance isn't super critical on this part as it's not used to developed the negative bias. Judging from the value of the caps around it it needs to be a fairly high in inductance  to filter the ac hum out. I'd go with this:   https://www.tubesandmore.com/products/fi...ma-300-ohm  If the level of hum is unreasonable add some capacitance to filter cap on the right side of this choke.