4. Competing Perfected Security Interests. When there is more than one perfected security interest, the security interests rank according to priority in time of filing or perfection. "Filing," of course, refers to the filing of an effective financing statement. "Perfection" refers to the acquisition of a perfected security interest, i.e., one that has attached and as to which any required perfection step has been taken. See Section 9-308 [Maine cite section 9-1308].

Example 1: On February 1, A files a financing statement covering a certain item of Debtor's equipment. On March 1, B files a financing statement covering the same equipment. On April 1, B makes a loan to Debtor and obtains a security interest in the equipment. On May 1, A makes a loan to Debtor and obtains a security interest in the same collateral. A has priority even though B's loan was made earlier and was perfected when made. It makes no difference whether A knew of B's security interest when A made its advance.

The problem stated in Example 1 is peculiar to a notice-filing system under which filing may occur before the security interest attaches (see Section 9-502 [Maine cite section 9-1502]). The justification for determining priority by order of filing lies in the necessity of protecting the filing system-that is, of allowing the first secured party who has filed to make subsequent advances without each time having to check for subsequent filings as a condition of protection. Note, however, that this first-to- file protection is not absolute. For example, Section 9-324 [Maine cite section 9-1324] affords priority to certain purchase- money security interests, even if a competing secured party was the first to file or perfect.

Example 2: A and B make nonpurchase-money advances secured by the same collateral. The collateral is in Debtor's possession, and neither security interest is perfected when the second advance is made. Whichever secured party first perfects its security interest (by taking possession of the collateral or by filing) takes priority. It makes no difference whether that secured party knows of the other security interest at the time it perfects its own.