Am 11.12.2016 um 23:00 schrieb George Matysiak:

My undated Full range is 1-63. I have one series with 20 observations
and another series with 15 observations, the first with (63-20) = 43
missing observations and the second with (63-15)= 48 missing
obseravations. There is no overlap in their respective observation
number. What would be best way to combine both series into one series
with 35 observations? Thanks.

If I understand correctly, the ordering doesn't matter (undated). And there is no overlap, so strict complementarity, so to speak.
Then what about:

smpl x --no-missing
series temp = x
smpl y --no-missing --replace
temp = y
smpl --full
series result = temp

(untested, and perhaps some typos included)