http://www.coincircuit.com/Philatel...ext=&page=22China, 1946, Second Shanghai Union surcharge on Martyr, Peking printing, $70 on 13˘ blue green (Chan 906. Scott 657A), full o.g., Fine to Very Fine, scarce issue.
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We can list Chu Chih-Hsin as follows:
1932-34----Scott no. 318* Blue green,perf.14 (no Wmk.) secret mark:two characteres not joined
1940-41----Scott no. 411 dp yellow green,perf.12 1/2,13 & Comp. (Wmk.261)secret mark:two characters joined
---Scott no. 430 dp yellow green,perf.12 1/2,13 & Comp. (no Wmk.)secret mark:two characters joined
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Surcharged stamps
1946-47-----Scott no.650(411) (Wmk.261)
-----Scott no.657A(318)* (no Wmk.) (on Peking Printing)
-----Scott no.658(430) (no Wmk.)
So your strip of three has the secret mark of two joined characters.
We can exclude scott 657A.That leaves Scott no.650 & 658.As rod222 pointed out, Wmk or no Wmk,
that is the question.