3. Secured Party's Right to Identifiable Proceeds. Under subsection (a)(2) [Maine cite subsection (1), paragraph (b)], which derives from former Section 9-306(2), a security interest attaches to any identifiable "proceeds," as defined in Section 9- 102 [Maine cite section 9-1102]. See also Section 9-203(f) [Maine cite section 9-1203, subsection (6)]. Subsection (b) [Maine cite subsection (2)] is new. It indicates when proceeds commingled with other property are identifiable proceeds and permits the use of whatever methods of tracing other law permits with respect to the type of property involved. Among the "equitable principles" whose use other law may permit is the "lowest intermediate balance rule." See Restatement (2d), Trusts §202.

4. Automatic Perfection in Proceeds: General Rule. Under subsection (c) [Maine cite subsection (3)], a security interest in proceeds is a perfected security interest if the security interest in the original collateral was perfected. This Article extends the period of automatic perfection in proceeds from ten days to 20 days. Generally, a security interest in proceeds becomes unperfected on the 21st day after the security interest attaches to the proceeds. See subsection (d) [Maine cite subsection (4)]. The loss of perfected status under subsection (d) [Maine cite subsection (4)] is prospective only. Compare, e.g., Section 9-515(c) [Maine cite section 9-1515, subsection (3)] (deeming security interest unperfected retroactively).

5. Automatic Perfection in Proceeds: Proceeds Acquired with Cash Proceeds. Subsection (d)(1) [Maine cite subsection (4), paragraph (a)] derives from former Section 9-306(3)(a). It carries forward the basic rule that a security interest in proceeds remains perfected beyond the period of automatic perfection if a filed financing statement covers the original collateral (e.g., inventory) and the proceeds are collateral in which a security interest may be perfected by filing in the office where the financing statement has been filed (e.g., equipment). A different rule applies if the proceeds are acquired with cash proceeds, as is the case if the original collateral (inventory) is sold for cash (cash proceeds) that is used to purchase equipment (proceeds). Under these circumstances, the security interest in the equipment proceeds remains perfected only if the description in the filed financing indicates the type of property constituting the proceeds (e.g., "equipment").