Symbian Signed was created in response to the mobile market’s requests for a certification program to promote best practise in application design for Symbian OS phones and to establish a formal link between an application and its origin. Increasingly, a verifiable signature is being demanded before an application is distributed.Symbian Signed is designed to address the needs of the entire mobile applications community: from software vendors (ISVs), through distribution channels, phone makers and operators to end-users (mobile phone subscribers).

If you are developer, before you deliver you project to test house for final Symbian Signed, the best way is to get a develop certificate for your project testing and verification on target.(becasuse, one time of final Symbian Signed, one time of pay for it, and expensive!).
How to apply certificate of Manufacturer Caps for developer? Look followed…
Pre-requirement:
1. you should get acs-key and acs-cer.
2. install Symbian Developer certificate request wizard
Symbian Developer certificate request wizard Version V1.9
Step:
1. produce *.csr file

2. enter your IMEIs, if you selected "Enable Phone Manufacturer Caps/unlimited IMEIs", the number of IMEI is unlimited, but at later, your reason maybe is required.

3. next, then your *.csr is completed.
4. go to www.symbiansigned.com
5. login using you account
6. my symbian signed ->developer certificates ->request ->Request Phone Manufacturer Approved DevCert (at the bottom of window)
7. step by step according to guide, and upload your *.csr, then application is OK!
8. after 3days or so, you can check the processing of approve.
Then congratulations, you got the certificate successfully!