In Unitrade also 1/2c is specified with Bothwell watermark. On my resource done I find that except the 1/2C all the others have the watermark, in fact we talk about all stamps printed sometimes in 1868.(I do not include the orange 1c,5c and 15c)
I reproduce what is wrote in THE STAMPS OF CANADA By BERTRAM W. H. POOLE (bayed 1$ from old book store):
The letters are large double lined capitals 12 H mm. high with the exception of the initial letters E, C and B upper line, which are 13 mm. high. The "watermark" is, of course, the trade-mark of the paper manufacturer and, like other watermarks of a similar nature, it is not of very great philatelic importance. It is very generally presumed that the paper watermarked in this manner was used provisionally-an opinion with which Mr. Howe seems to concur by his statement that "the watermarked paper must been used sometime during the year 1868, probably the middle, when supplies of all values except the l/2c were printed."
I agrees that the stamps become officially on first of April 1868. Then the supply was further done by Bothwell paper.
Conclusion: With or not watermark, the stamps are common series.
The watermark exists on the 1/2c and the 15c, too. The 1/2c is the rarest, the 15c is scarce. Although originally produced early on in the issue, stocks were kept unused due to poor quality and used throughout the period of the Large Queens when stock quantities were low.
Guys I make a studies of the first Canadian stamps till 1930. I kook of what we know today compared with that time reports. I look also of the imperforare was issued or they are just wasting papers took by some one. ( EX 5 cent king, officially only 2 or 3 cent(sorry for mix-up denomination).
Why, because for me, (personal opinion) only official stamps have place in a collection.