Prior to Heath Company being purchased by Zenith Data Systems (ZDS), Heath offered an assembled H89 as the WH89. The "W" most likely referred to 'Wired', vs. the H-89 which came in kit version.
Identical to Heath Company's H89 kit computer, but the WH89 came factory assembled.
From the 1979 Heath Catalog:
WH89 Completely Assembled All-In-One Computer with floppy disk system. Does not include H88-5 Audio Cassette Interface....... 2295.00
This early system came with only 16K of RAM.